diff --git a/src/calibre/ebooks/oeb/polish/report.py b/src/calibre/ebooks/oeb/polish/report.py
new file mode 100644
index 0000000000..0d6dc4a3d4
--- /dev/null
+++ b/src/calibre/ebooks/oeb/polish/report.py
@@ -0,0 +1,44 @@
+#!/usr/bin/env python
+# vim:fileencoding=utf-8
+from __future__ import (unicode_literals, division, absolute_import,
+                        print_function)
+
+__license__ = 'GPL v3'
+__copyright__ = '2015, Kovid Goyal <kovid at kovidgoyal.net>'
+
+import posixpath, os
+from collections import namedtuple
+
+from calibre.ebooks.oeb.polish.container import OEB_DOCS, OEB_STYLES, OEB_FONTS
+
+File = namedtuple('File', 'name dir basename size category')
+
+def get_category(name, mt):
+    category = 'misc'
+    if mt.startswith('image/'):
+        category = 'image'
+    elif mt in OEB_FONTS:
+        category = 'font'
+    elif mt in OEB_STYLES:
+        category = 'style'
+    elif mt in OEB_DOCS:
+        category = 'text'
+    ext = name.rpartition('.')[-1].lower()
+    if ext in {'ttf', 'otf', 'woff'}:
+        # Probably wrong mimetype in the OPF
+        category = 'font'
+    elif ext == 'opf':
+        category = 'opf'
+    elif ext == 'ncx':
+        category = 'toc'
+    return category
+
+def file_data(container):
+    for name, path in container.name_path_map.iteritems():
+        yield File(name, posixpath.dirname(name), os.path.getsize(name), posixpath.basename(name),
+                   get_category(name, container.mime_map.get(name, '')))
+
+
+def gather_data(container):
+    data =  {'files':tuple(file_data(container))}
+    return data
diff --git a/src/calibre/gui2/tweak_book/reports.py b/src/calibre/gui2/tweak_book/reports.py
new file mode 100644
index 0000000000..107ad76686
--- /dev/null
+++ b/src/calibre/gui2/tweak_book/reports.py
@@ -0,0 +1,134 @@
+#!/usr/bin/env python
+# vim:fileencoding=utf-8
+from __future__ import (unicode_literals, division, absolute_import,
+                        print_function)
+
+__license__ = 'GPL v3'
+__copyright__ = '2015, Kovid Goyal <kovid at kovidgoyal.net>'
+
+from threading import Thread
+from future_builtins import map
+from operator import itemgetter
+
+from PyQt5.Qt import (
+    QSize, QStackedLayout, QLabel, QVBoxLayout, Qt, QWidget, pyqtSignal,
+    QAbstractTableModel)
+
+from calibre.gui2 import error_dialog
+from calibre.gui2.tweak_book import current_container
+from calibre.gui2.tweak_book.widgets import Dialog
+from calibre.gui2.progress_indicator import ProgressIndicator
+from calibre.ebooks.oeb.polish.report import gather_data
+
+class FilesModel(QAbstractTableModel):
+
+    COLUMN_HEADERS = [_('Folder'), _('Name'), _('Size (KB)'), _('Type')]
+    CATEGORY_NAMES = {
+        'image':_('Image'),
+        'text': _('Text'),
+        'font': _('Font'),
+        'style': _('Style'),
+        'opf': _('Metadata'),
+        'toc': _('Table of Contents'),
+    }
+
+    def __init__(self, parent=None):
+        self.files = ()
+        self.total_size = self.text_count = self.style_count = 0
+        QAbstractTableModel.__init__(self, parent)
+
+    def columnCount(self, parent=None):
+        return len(self.COLUMN_HEADERS)
+
+    def rowCount(self, parent=None):
+        return len(self.files)
+
+    def headerData(self, section, orientation, role=Qt.DisplayRole):
+        if role == Qt.DisplayRole and orientation == Qt.Horizontal:
+            try:
+                return self.COLUMN_HEADERS[section]
+            except IndexError:
+                pass
+        return QAbstractTableModel.headerData(self, section, orientation, role)
+
+    def __call__(self, data):
+        self.beginResetModel()
+        self.files = data['files']
+        self.total_size = sum(map(itemgetter(3), self.files))
+        self.text_count = sum(1 for f in self.files if f.category == 'text')
+        self.style_count = sum(1 for f in self.files if f.category == 'style')
+        self.endResetModel()
+
+    def data(self, index, role=Qt.DisplayRole):
+        if role == Qt.DisplayRole:
+            try:
+                entry = self.files[index.row()]
+            except IndexError:
+                return None
+            col = index.column()
+            if col == 0:
+                return entry.dir
+            if col == 1:
+                return entry.basename
+            if col == 2:
+                sz = entry.size / 1024.
+                return ('%.2f' % sz if int(sz) != sz else type('')(sz))
+            if col == 3:
+                return self.CATEGORY_NAMES.get(entry.category)
+
+class Reports(Dialog):
+
+    data_gathered = pyqtSignal(object, object)
+
+    def __init__(self, parent=None):
+        Dialog.__init__(self, _('Reports'), 'reports-dialog', parent=parent)
+        self.data_gathered.connect(self.display_data, type=Qt.QueuedConnection)
+
+    def setup_ui(self):
+        self.wait_stack = s = QStackedLayout(self)
+
+        self.pw = pw = QWidget(self)
+        s.addWidget(pw)
+        pw.l = l = QVBoxLayout(pw)
+        self.pi = pi = ProgressIndicator(self, 256)
+        l.addStretch(1), l.addWidget(pi, alignment=Qt.AlignHCenter), l.addSpacing(10)
+        pw.la = la = QLabel(_('Gathering data, please wait...'))
+        la.setStyleSheet('QLabel { font-size: 30pt; font-weight: bold }')
+        l.addWidget(la, alignment=Qt.AlignHCenter), l.addStretch(1)
+
+    def sizeHint(self):
+        return QSize(950, 600)
+
+    def refresh(self):
+        self.wait_stack.setCurrentIndex(0)
+        self.pi.startAnimation()
+        t = Thread(name='GatherReportData', target=self.gather_data)
+        t.daemon = True
+        t.start()
+
+    def gather_data(self):
+        try:
+            ok, data = True, gather_data(current_container())
+        except Exception:
+            import traceback
+            ok, data = False, traceback.format_exc()
+        self.data_gathered.emit(ok, data)
+
+    def display_data(self, ok, data):
+        self.wait_stack.setCurrentIndex(1)
+        if not ok:
+            return error_dialog(self, _('Failed to gather data'), _(
+                'Failed to gather data for the report. Click "Show details" for more'
+                ' information.'), det_msg=data, show=True)
+
+
+if __name__ == '__main__':
+    from calibre.gui2 import Application
+    app = Application([])
+    from calibre.gui2.tweak_book import set_current_container
+    from calibre.gui2.tweak_book.boss import get_container
+    set_current_container(get_container('/t/demo.epub'))
+    d = Reports()
+    d.refresh()
+    d.exec_()
+    del d, app