diff --git a/src/calibre/debug.py b/src/calibre/debug.py
index 3a080fc57b..86a0477811 100644
--- a/src/calibre/debug.py
+++ b/src/calibre/debug.py
@@ -51,6 +51,8 @@ Run an embedded python interpreter.
             'with sqlite3 works.')
     parser.add_option('-p', '--py-console', help='Run python console',
             default=False, action='store_true')
+    parser.add_option('-m', '--inspect-mobi',
+            help='Inspect the MOBI file at the specified path', default=None)
 
     return parser
 
@@ -227,6 +229,9 @@ def main(args=sys.argv):
         if len(args) > 1 and os.access(args[-1], os.R_OK):
             sql_dump = args[-1]
         reinit_db(opts.reinitialize_db, sql_dump=sql_dump)
+    elif opts.inspect_mobi is not None:
+        from calibre.ebooks.mobi.debug import inspect_mobi
+        inspect_mobi(opts.inspect_mobi)
     else:
         from calibre import ipython
         ipython()
diff --git a/src/calibre/ebooks/mobi/debug.py b/src/calibre/ebooks/mobi/debug.py
new file mode 100644
index 0000000000..13a8e204bb
--- /dev/null
+++ b/src/calibre/ebooks/mobi/debug.py
@@ -0,0 +1,375 @@
+#!/usr/bin/env python
+# vim:fileencoding=UTF-8:ts=4:sw=4:sta:et:sts=4:ai
+from __future__ import (unicode_literals, division, absolute_import,
+                        print_function)
+
+__license__   = 'GPL v3'
+__copyright__ = '2011, Kovid Goyal <kovid@kovidgoyal.net>'
+__docformat__ = 'restructuredtext en'
+
+import struct, datetime
+from calibre.utils.date import utc_tz
+from calibre.ebooks.mobi.langcodes import main_language, sub_language
+
+class PalmDOCAttributes(object):
+
+    class Attr(object):
+
+        def __init__(self, name, field, val):
+            self.name = name
+            self.val = val & field
+
+        def __str__(self):
+            return '%s: %s'%(self.name, bool(self.val))
+
+    def __init__(self, raw):
+        self.val = struct.unpack(b'<H', raw)[0]
+        self.attributes = []
+        for name, field in [('Read Only', 0x02), ('Dirty AppInfoArea', 0x04),
+                ('Backup this database', 0x08),
+                ('Okay to install newer over existing copy, if present on PalmPilot', 0x10),
+                ('Force the PalmPilot to reset after this database is installed', 0x12),
+                ('Don\'t allow copy of file to be beamed to other Pilot',
+                    0x14)]:
+            self.attributes.append(PalmDOCAttributes.Attr(name, field,
+                self.val))
+
+    def __str__(self):
+        attrs = '\n\t'.join([str(x) for x in self.attributes])
+        return 'PalmDOC Attributes: %s\n\t%s'%(bin(self.val), attrs)
+
+class PalmDB(object):
+
+    def __init__(self, raw):
+        self.raw = raw
+
+        if self.raw.startswith(b'TPZ'):
+            raise ValueError('This is a Topaz file')
+
+        self.name     = self.raw[:32].replace(b'\x00', b'')
+        self.attributes = PalmDOCAttributes(self.raw[32:34])
+        self.version = struct.unpack(b'>H', self.raw[34:36])[0]
+
+        palm_epoch = datetime.datetime(1904, 1, 1, tzinfo=utc_tz)
+        self.creation_date_raw = struct.unpack(b'>I', self.raw[36:40])[0]
+        self.creation_date = (palm_epoch +
+                datetime.timedelta(seconds=self.creation_date_raw))
+        self.modification_date_raw = struct.unpack(b'>I', self.raw[40:44])[0]
+        self.modification_date = (palm_epoch +
+                datetime.timedelta(seconds=self.modification_date_raw))
+        self.last_backup_date_raw = struct.unpack(b'>I', self.raw[44:48])[0]
+        self.last_backup_date = (palm_epoch +
+                datetime.timedelta(seconds=self.last_backup_date_raw))
+        self.modification_number = struct.unpack(b'>I', self.raw[48:52])[0]
+        self.app_info_id = self.raw[52:56]
+        self.sort_info_id = self.raw[56:60]
+        self.type = self.raw[60:64]
+        self.creator = self.raw[64:68]
+        self.ident = self.type + self.creator
+        if self.ident not in (b'BOOKMOBI', b'TEXTREAD'):
+            raise ValueError('Unknown book ident: %r'%self.ident)
+        self.uid_seed = self.raw[68:72]
+        self.next_rec_list_id = self.raw[72:76]
+
+        self.number_of_records, = struct.unpack(b'>H', self.raw[76:78])
+
+    def __str__(self):
+        ans = ['*'*20 + ' PalmDB Header '+ '*'*20]
+        ans.append('Name: %r'%self.name)
+        ans.append(str(self.attributes))
+        ans.append('Version: %s'%self.version)
+        ans.append('Creation date: %s (%s)'%(self.creation_date.isoformat(),
+            self.creation_date_raw))
+        ans.append('Modification date: %s (%s)'%(self.modification_date.isoformat(),
+            self.modification_date_raw))
+        ans.append('Backup date: %s (%s)'%(self.last_backup_date.isoformat(),
+            self.last_backup_date_raw))
+        ans.append('Modification number: %s'%self.modification_number)
+        ans.append('App Info ID: %r'%self.app_info_id)
+        ans.append('Sort Info ID: %r'%self.sort_info_id)
+        ans.append('Type: %r'%self.type)
+        ans.append('Creator: %r'%self.creator)
+        ans.append('UID seed: %r'%self.uid_seed)
+        ans.append('Next record list id: %r'%self.next_rec_list_id)
+        ans.append('Number of records: %s'%self.number_of_records)
+
+        return '\n'.join(ans)
+
+class Record(object):
+
+    def __init__(self, raw, header):
+        self.offset, self.flags, self.uid = header
+        self.raw = raw
+
+    @property
+    def header(self):
+        return 'Offset: %d Flags: %d UID: %d'%(self.offset, self.flags,
+                self.uid)
+
+class EXTHRecord(object):
+
+    def __init__(self, type_, data):
+        self.type = type_
+        self.data = data
+        self.name = {
+                1 : 'DRM Server id',
+                2 : 'DRM Commerce id',
+                3 : 'DRM ebookbase book id',
+                100 : 'author',
+                101 : 'publisher',
+                102 : 'imprint',
+                103 : 'description',
+                104 : 'isbn',
+                105 : 'subject',
+                106 : 'publishingdate',
+                107 : 'review',
+                108 : 'contributor',
+                109 : 'rights',
+                110 : 'subjectcode',
+                111 : 'type',
+                112 : 'source',
+                113 : 'asin',
+                114 : 'versionnumber',
+                115 : 'sample',
+                116 : 'startreading',
+                117 : 'adult',
+                118 : 'retailprice',
+                119 : 'retailpricecurrency',
+                201 : 'coveroffset',
+                202 : 'thumboffset',
+                203 : 'hasfakecover',
+                204 : 'Creator Software',
+                205 : 'Creator Major Version', # '>I'
+                206 : 'Creator Minor Version', # '>I'
+                207 : 'Creator Build number', # '>I'
+                208 : 'watermark',
+                209 : 'tamper_proof_keys',
+                300 : 'fontsignature',
+                301 : 'clippinglimit', # percentage '>B'
+                402 : 'publisherlimit',
+                404 : 'TTS flag', # '>B' 1 - TTS disabled 0 - TTS enabled
+                501 : 'cdetype', # 4 chars (PDOC or EBOK)
+                502 : 'lastupdatetime',
+                503 : 'updatedtitle',
+        }.get(self.type, repr(self.type))
+
+    def __str__(self):
+        return '%s (%d): %r'%(self.name, self.type, self.data)
+
+class EXTHHeader(object):
+
+    def __init__(self, raw):
+        self.raw = raw
+        if not self.raw.startswith(b'EXTH'):
+            raise ValueError('EXTH header does not start with EXTH')
+        self.length, = struct.unpack(b'>I', self.raw[4:8])
+        self.count,  = struct.unpack(b'>I', self.raw[8:12])
+
+        pos = 12
+        self.records = []
+        for i in xrange(self.count):
+            pos = self.read_record(pos)
+
+    def read_record(self, pos):
+        type_, length = struct.unpack(b'>II', self.raw[pos:pos+8])
+        data = self.raw[pos+8:pos+length-8]
+        self.records.append(EXTHRecord(type_, data))
+        return pos + length
+
+    def __str__(self):
+        ans = ['*'*20 + ' EXTH Header '+ '*'*20]
+        ans.append('EXTH header length: %d'%self.length)
+        ans.append('Number of EXTH records: %d'%self.count)
+        ans.append('EXTH records...')
+        for r in self.records:
+            ans.append(str(r))
+        return '\n'.join(ans)
+
+
+class MOBIHeader(object):
+
+    def __init__(self, record0):
+        self.raw = record0.raw
+
+        self.compression_raw = self.raw[:2]
+        self.compression = {1: 'No compression', 2: 'PalmDoc compression',
+                17480: 'HUFF/CDIC compression'}.get(struct.unpack(b'>H',
+                    self.compression_raw)[0],
+                    repr(self.compression_raw))
+        self.unused = self.raw[2:4]
+        self.text_length, = struct.unpack(b'>I', self.raw[4:8])
+        self.number_of_text_records, self.text_record_size = \
+                struct.unpack(b'>HH', self.raw[8:12])
+        self.encryption_type_raw, = struct.unpack(b'>H', self.raw[12:14])
+        self.encryption_type = {0: 'No encryption',
+                1: 'Old mobipocket encryption',
+                2:'Mobipocket encryption'}.get(self.encryption_type_raw,
+                repr(self.encryption_type_raw))
+        self.unknown = self.raw[14:16]
+
+        self.identifier = self.raw[16:20]
+        if self.identifier != b'MOBI':
+            raise ValueError('Identifier %r unknown'%self.identifier)
+
+        self.length, = struct.unpack(b'>I', self.raw[20:24])
+        self.type_raw, = struct.unpack(b'>I', self.raw[24:28])
+        self.type = {
+                2 : 'Mobipocket book',
+                3 : 'PalmDOC book',
+                4 : 'Audio',
+                257 : 'News',
+                258 : 'News Feed',
+                259 : 'News magazine',
+                513 : 'PICS',
+                514 : 'Word',
+                515 : 'XLS',
+                516 : 'PPT',
+                517 : 'TEXT',
+                518 : 'HTML',
+            }.get(self.type_raw, repr(self.type_raw))
+
+        self.encoding_raw, = struct.unpack(b'>I', self.raw[28:32])
+        self.encoding = {
+                1252 : 'cp1252',
+                65001: 'utf-8',
+            }.get(self.encoding_raw, repr(self.encoding_raw))
+        self.uid = self.raw[32:36]
+        self.file_version = struct.unpack(b'>I', self.raw[36:40])
+        self.reserved = self.raw[40:80]
+        self.first_non_book_record, = struct.unpack(b'>I', self.raw[80:84])
+        self.fullname_offset, = struct.unpack(b'>I', self.raw[84:88])
+        self.fullname_length, = struct.unpack(b'>I', self.raw[88:92])
+        self.locale_raw, = struct.unpack(b'>I', self.raw[92:96])
+        langcode = self.locale_raw
+        langid    = langcode & 0xFF
+        sublangid = (langcode >> 10) & 0xFF
+        self.language = main_language.get(langid, 'ENGLISH')
+        self.sublanguage = sub_language.get(sublangid, 'NEUTRAL')
+
+        self.input_language = self.raw[96:100]
+        self.output_langauage = self.raw[100:104]
+        self.min_version, = struct.unpack(b'>I', self.raw[104:108])
+        self.first_image_index, = struct.unpack(b'>I', self.raw[108:112])
+        self.huffman_record_offset, = struct.unpack(b'>I', self.raw[112:116])
+        self.huffman_record_count, = struct.unpack(b'>I', self.raw[116:120])
+        self.unknown2 = self.raw[120:128]
+        self.exth_flags, = struct.unpack(b'>I', self.raw[128:132])
+        self.has_exth = bool(self.exth_flags & 0x40)
+        self.has_drm_data = self.length >= 184 and len(self.raw) >= 184
+        if self.has_drm_data:
+            self.unknown3 = self.raw[132:164]
+            self.drm_offset, = struct.unpack(b'>I', self.raw[164:168])
+            self.drm_count, = struct.unpack(b'>I', self.raw[168:172])
+            self.drm_size, = struct.unpack(b'>I', self.raw[172:176])
+            self.drm_flags = bin(struct.unpack(b'>I', self.raw[176:180])[0])
+        self.has_extra_data_flags = self.length >= 244 and len(self.raw) >= 244
+        if self.has_extra_data_flags:
+            self.unknown4 = self.raw[180:242]
+            self.extra_data_flags = bin(struct.unpack(b'>H',
+                self.raw[242:244])[0])
+
+        if self.has_exth:
+            self.exth_offset = 16 + self.length
+
+            self.exth = EXTHHeader(self.raw[self.exth_offset:])
+
+            self.end_of_exth = self.exth_offset + self.exth.length
+            self.bytes_after_exth = len(self.raw) - self.end_of_exth
+
+    def __str__(self):
+        ans = ['*'*20 + ' MOBI Header '+ '*'*20]
+        ans.append('Compression: %s'%self.compression)
+        ans.append('Unused: %r'%self.unused)
+        ans.append('Number of text records: %d'%self.number_of_text_records)
+        ans.append('Text record size: %d'%self.text_record_size)
+        ans.append('Encryption: %s'%self.encryption_type)
+        ans.append('Unknown: %r'%self.unknown)
+        ans.append('Identifier: %r'%self.identifier)
+        ans.append('Header length: %d'% self.length)
+        ans.append('Type: %s'%self.type)
+        ans.append('Encoding: %s'%self.encoding)
+        ans.append('UID: %r'%self.uid)
+        ans.append('File version: %d'%self.file_version)
+        ans.append('Reserved: %r'%self.reserved)
+        ans.append('First non-book record: %d'% self.first_non_book_record)
+        ans.append('Full name offset: %d'%self.fullname_offset)
+        ans.append('Full name length: %d bytes'%self.fullname_length)
+        ans.append('Langcode: %r'%self.locale_raw)
+        ans.append('Language: %s'%self.language)
+        ans.append('Sub language: %s'%self.sublanguage)
+        ans.append('Input language: %r'%self.input_language)
+        ans.append('Output language: %r'%self.output_langauage)
+        ans.append('Min version: %d'%self.min_version)
+        ans.append('First Image index: %d'%self.first_image_index)
+        ans.append('Huffman record offset: %d'%self.huffman_record_offset)
+        ans.append('Huffman record count: %d'%self.huffman_record_count)
+        ans.append('Unknown2: %r'%self.unknown2)
+        ans.append('EXTH flags: %r (%s)'%(self.exth_flags, self.has_exth))
+        if self.has_drm_data:
+            ans.append('Unknown3: %r'%self.unknown3)
+            ans.append('DRM Offset: %s'%self.drm_offset)
+            ans.append('DRM Count: %s'%self.drm_count)
+            ans.append('DRM Size: %s'%self.drm_size)
+            ans.append('DRM Flags: %r'%self.drm_flags)
+        if self.has_extra_data_flags:
+            ans.append('Unknown4: %r'%self.unknown4)
+            ans.append('Extra data flags: %r'%self.extra_data_flags)
+
+        ans = '\n'.join(ans)
+
+        if self.has_exth:
+            ans += '\n\n' + str(self.exth)
+            ans += '\n\nBytes after EXTH: %d'%self.bytes_after_exth
+
+        return ans
+
+class MOBIFile(object):
+
+    def __init__(self, stream):
+        self.raw = stream.read()
+
+        self.palmdb = PalmDB(self.raw[:78])
+
+        self.record_headers = []
+        self.records = []
+        for i in xrange(self.palmdb.number_of_records):
+            pos = 78 + i * 8
+            offset, a1, a2, a3, a4 = struct.unpack(b'>LBBBB', self.raw[pos:pos+8])
+            flags, val = a1, a2 << 16 | a3 << 8 | a4
+            self.record_headers.append((offset, flags, val))
+
+        def section(section_number):
+            if section_number == self.palmdb.number_of_records - 1:
+                end_off = len(self.raw)
+            else:
+                end_off = self.record_headers[section_number + 1][0]
+            off = self.record_headers[section_number][0]
+            return self.raw[off:end_off]
+
+        for i in range(self.palmdb.number_of_records):
+            self.records.append(Record(section(i), self.record_headers[i]))
+
+        self.mobi_header = MOBIHeader(self.records[0])
+
+
+    def print_header(self):
+        print (str(self.palmdb).encode('utf-8'))
+        print ()
+        print ('Record headers:')
+        for i, r in enumerate(self.records):
+            print ('%6d. %s'%(i, r.header))
+
+        print ()
+        print (str(self.mobi_header).encode('utf-8'))
+
+def inspect_mobi(path_or_stream):
+    stream = (path_or_stream if hasattr(path_or_stream, 'read') else
+            open(path_or_stream, 'rb'))
+    f = MOBIFile(stream)
+    f.print_header()
+
+if __name__ == '__main__':
+    import sys
+    f = MOBIFile(open(sys.argv[1], 'rb'))
+    f.print_header()
+