diff --git a/src/calibre/srv/render_book.py b/src/calibre/srv/render_book.py
index a372a48e6c..6316e11bf9 100644
--- a/src/calibre/srv/render_book.py
+++ b/src/calibre/srv/render_book.py
@@ -69,7 +69,7 @@ class Container(ContainerBase):
         self.virtualize_resources()
         def manifest_data(name):
             return {'size':os.path.getsize(self.name_path_map[name]), 'is_virtualized': name in self.virtualized_names}
-        data['manifest'] = {name:manifest_data(name) for name in set(self.name_path_map) - excluded_names},
+        data['files'] = {name:manifest_data(name) for name in set(self.name_path_map) - excluded_names}
         self.commit()
         for name in excluded_names:
             os.remove(self.name_path_map[name])
diff --git a/src/pyj/ajax.pyj b/src/pyj/ajax.pyj
index b58ce7ff5d..f2492a09ab 100644
--- a/src/pyj/ajax.pyj
+++ b/src/pyj/ajax.pyj
@@ -18,7 +18,7 @@ def encode_query(query):
             has_query = True
     return path
 
-def ajax(path, on_complete, on_progress=None, bypass_cache=True, method='GET', query=None, timeout=30*1000, ok_code=200):
+def ajax(path, on_complete, on_progress=None, bypass_cache=True, method='GET', query=None, timeout=30*1000, ok_code=200, progress_totals_needed=True):
     # Run an AJAX request. on_complete must be a function that accepts three
     # arguments: end_type, xhr, ev where end_type is one of 'abort', 'error',
     # 'load', 'timeout'. In case end_type is anything other than 'load' you can
@@ -51,6 +51,9 @@ def ajax(path, on_complete, on_progress=None, bypass_cache=True, method='GET', q
         if ev.lengthComputable:
             on_progress(ev.loaded, ev.total, xhr)
         elif ev.loaded:
+            if not progress_totals_needed:
+                on_progress(ev.loaded, undefined, xhr)
+                return
             ul = xhr.getResponseHeader('Calibre-Uncompressed-Length')
             if ul:
                 try:
diff --git a/src/pyj/read_book/db.pyj b/src/pyj/read_book/db.pyj
index 9f4b94b86e..d1b05ff2d0 100644
--- a/src/pyj/read_book/db.pyj
+++ b/src/pyj/read_book/db.pyj
@@ -2,7 +2,6 @@
 # License: GPL v3 Copyright: 2016, Kovid Goyal <kovid at kovidgoyal.net>
 
 from gettext import gettext as _
-from modals import error_dialog
 
 def upgrade_schema(idb, old_version, new_version):
     print('upgrade_schema:', old_version, new_version)
@@ -21,6 +20,7 @@ class DB:
         self.supports_blobs = supports_blobs
         if not supports_blobs:
             print('IndexedDB does not support Blob storage, using base64 encoding instead')
+        self.show_error = ui.show_error.bind(ui)
 
         idb.onerror = def(event):
             self.display_error(None, event)
@@ -31,7 +31,7 @@ class DB:
 
         idb.onversionchange = def(event):
             idb.close()
-            error_dialog(_('Database upgraded!'), _(
+            ui.show_error(_('Database upgraded!'), _(
                 'A newer version of calibre is available, please click the reload button in your browser.'))
 
     def display_error(self, msg, event):
@@ -46,7 +46,7 @@ class DB:
             desc = desc.error.toString()
         elif desc.errorCode:
             desc = desc.errorCode
-        error_dialog(_('Cannot read book'), msg, desc)
+        self.show_error(_('Cannot read book'), msg, desc)
 
     def do_op(self, stores, data, error_msg, proceed, op='get', store=None):
         store = store or stores[0]
@@ -71,7 +71,7 @@ class DB:
             proceed(result or {
                 'key':key,
                 'is_complete':False,
-                'stores_blobs': True,
+                'b64_encoded_files': v'[]',
                 'book_hash':None,
                 'last_read': Date(),
                 'metadata': metadata,
@@ -84,10 +84,14 @@ class DB:
         book.metadata = manifest.metadata
         book.book_hash = manifest.book_hash.hash
         book.is_complete = False
-        book.stores_blobs = True
+        book.b64_encoded_files = v'[]'
+        book.is_complete = False
         v'delete manifest["metadata"]'
         self.do_op(['books'], book, _('Failed to write to the books database'), proceed, op='put')
 
+    def store_file(self, book, fname, xhr):
+        pass
+
 def create_db(ui, interface_data):
     if not window.indexedDB:
         ui.db = _('Your browser does not support IndexedDB. Cannot read books. Consider using a modern browser, such as Firefox, Chrome or Edge.')
diff --git a/src/pyj/read_book/ui.pyj b/src/pyj/read_book/ui.pyj
index b3a23e285f..fc502328b0 100644
--- a/src/pyj/read_book/ui.pyj
+++ b/src/pyj/read_book/ui.pyj
@@ -1,9 +1,11 @@
 # vim:fileencoding=utf-8
 # License: GPL v3 Copyright: 2016, Kovid Goyal <kovid at kovidgoyal.net>
 
-from ajax import ajax
+from ajax import ajax, encode_query
+from elementmaker import E
 from gettext import gettext as _
 from modals import error_dialog
+from utils import human_readable
 from read_book.db import create_db
 
 RENDER_VERSION = 1  # Also change this in render_book.py
@@ -13,10 +15,71 @@ class ReadUI:
     def __init__(self, interface_data, container):
         self.interface_data = interface_data
         self.db = None
-        self.current_metadata = None
+        self.current_metadata = {'title': _('Unknown book')}
+        self.current_book_id = None
         self.manifest_xhr = None
         create_db(self, interface_data)
         self.pending_load = None
+        self.downloads_in_progress = []
+        self.progress_id = 'book-load-progress'
+        self.display_id = 'book-iframe-container'
+        self.error_id = 'book-global-error-container'
+        self.stacked_widgets = [self.progress_id, self.display_id, self.error_id]
+
+        container.appendChild(E.div(
+            id=self.progress_id, style='display:none; text-align: center',
+            E.h3(style='margin-top:30vh; margin-bottom: 1ex;'),
+            E.progress(style='margin: 1ex'),
+            E.div(style='margin: 1ex')
+        ))
+
+        container.appendChild(E.div(
+            id=self.error_id, style='display:none; text-align: center',
+            E.h2(_('Could not open book'), style='margin: 1ex; margin-top: 30vh;'),
+            E.div(style='margin: 1ex', E.a()),
+        ))
+
+        container.appendChild(E.div(
+            id=self.display_id, style='display:none',
+        ))
+
+    def show_stack(self, name):
+        ans = None
+        for w in self.stacked_widgets:
+            d = document.getElementById(w)
+            v = 'none'
+            if name is w:
+                ans = d
+                v = 'block'
+            d.style.display = v
+        return ans
+
+    def show_error(self, title, msg, details):
+        div = self.show_stack(self.error_id)
+        error_dialog(title, msg, details)
+        a = div.lastChild.firstChild
+        if self.current_book_id:
+            a.setAttribute('href', encode_query({
+                'library_id':self.interface_data.library_id,
+                'book-id': (self.current_book_id + ''),
+                'panel':'book-details'
+            }))
+            a.textContent = str.format(_(
+                'Click to go back to the details page for: {}'), self.current_metadata.title)
+        else:
+            a.textContent = ''
+            a.setAttribute('href', '')
+
+    def init_ui(self):
+        div = self.show_stack(self.progress_id)
+        if self.current_metadata:
+            div.firstChild.textContent = str.format(_(
+                'Downloading {0} for offline reading, please wait...'), self.current_metadata.title)
+        else:
+            div.firstChild.textContent = ''
+        pr = div.firstChild.nextSibling
+        pr.removeAttribute('value'), pr.removeAttribute('max')
+        div.lastChild.textContent = _('Downloading book manifest...')
 
     def load_book(self, book_id, fmt, metadata):
         if self.db is None:
@@ -31,18 +94,22 @@ class ReadUI:
             self.start_load(*pl)
 
     def start_load(self, book_id, fmt, metadata):
-        if type(self.db) is 'string':
-            error_dialog(_('Cannot read book'), self.db)
-            return
+        self.current_book_id = book_id
         metadata = metadata or self.interface_data.metadata[book_id]
-        self.current_metadata = metadata or {'title':_('Current Book')}
+        self.current_metadata = metadata or {'title':_('Book id #') + book_id}
+        self.init_ui()
+        if type(self.db) is 'string':
+            self.show_error(_('Cannot read book'), self.db)
+            return
         self.db.get_book(book_id, fmt, metadata, self.got_book.bind(self))
 
     def got_book(self, book):
-        if not book.manifest or book.manifest.version != RENDER_VERSION:
+        if not book.manifest or book.manifest.version != RENDER_VERSION or not book.is_complete:
+            # We re-download the manifest when the book is not complete to ensure we have the
+            # correct manifest, even though doing so is not strictly necessary
             self.get_manifest(book)
-            return
-        self.display_book(book) if book.is_complete else self.download_book(book)
+        else:
+            self.display_book(book)
 
     def get_manifest(self, book):
         library_id, book_id, fmt = book.key
@@ -58,23 +125,70 @@ class ReadUI:
         if end_type is 'abort':
             return
         if end_type is not 'load':
-            return error_dialog(_('Failed to load book manifest'), str.format(
+            return self.show_error(_('Failed to load book manifest'), str.format(
                 _('Could not open {title} as book manifest failed to load, click "Show Details" for more information.'), title=self.current_metadata.title),
                                 xhr.error_html)
         try:
             manifest = JSON.parse(xhr.responseText)
         except Exception as err:
-            return error_dialog(_('Failed to load book manifest'), str.format(
+            return self.show_error(_('Failed to load book manifest'), str.format(
                 _('The manifest for {title} is not valid'), title=self.current_metadata.title),
                                 err.stack or err.toString())
         if manifest.version != RENDER_VERSION:
-            return error_dialog(_('calibre upgraded!'), _(
+            return self.show_error(_('calibre upgraded!'), _(
                 'A newer version of calibre is available, please click the reload button in your browser.'))
         self.current_metadata = manifest.metadata
         self.db.save_manifest(book, manifest, self.download_book.bind(self, book))
 
     def download_book(self, book):
-        pass
+        files = book.manifest.files
+        total = 0
+        for name in files:
+            total += files[name].size
+        files_left = set(book.manifest.files)
+        failed_files = []
+        for xhr in self.downloads_in_progress:
+            xhr.abort()
+        self.downloads_in_progress = []
+        progress = document.getElementById(self.progress_id)
+        pbar = progress.firstChild.nextSibling
+        library_id, book_id, fmt = book.key
+        base_path = str.format(
+            'book-file/{}/{}/{}/{}/', encodeURIComponent(book_id), encodeURIComponent(fmt),
+            encodeURIComponent(book.manifest.book_hash.size), encodeURIComponent(book.manifest.book_hash.mtime))
+        query = {'library_id': library_id}
+        progress_track = {}
+        pbar.setAttribute('max', total + '')
+
+        def update_progress():
+            x = 0
+            for name in progress_track:
+                x += progress_track[name]
+            pbar.setAttribute('value', x + '')
+            progress.lastChild.textContent = str.format(_('Downloaded {0}, {1} left'), human_readable(x), human_readable(total - x))
+
+        def on_complete(end_type, xhr, ev):
+            self.downloads_in_progress.remove(xhr)
+            files_left.discard(this)
+            progress_track[this] = files[this].size
+            update_progress()
+            if end_type is 'abort':
+                return
+            if end_type is 'load':
+                self.db.store_file(book, fname, xhr)
+            else:
+                failed_files.append([this, xhr.error_html])
+            if len(files_left):
+                return
+
+        def on_progress(loaded):
+            progress_track[this] = loaded
+            update_progress()
+
+        for fname in files_left:
+            xhr = ajax(base_path + encodeURIComponent(fname), on_complete.bind(fname), on_progress=on_progress.bind(fname), query=query, progress_totals_needed=False)
+            xhr.send()
+            self.downloads_in_progress.append(xhr)
 
     def display_book(self, book):
-        pass
+        self.show_stack(self.display_id)
diff --git a/src/pyj/utils.pyj b/src/pyj/utils.pyj
index 3b7ed51e50..82d391b9d2 100644
--- a/src/pyj/utils.pyj
+++ b/src/pyj/utils.pyj
@@ -79,5 +79,20 @@ def fmt_sidx(val, fmt='{:.2f}', use_roman=True):
         return int(val) + ''
     return str.format(fmt, float(val))
 
+def human_readable(size, sep=' '):
+    divisor, suffix = 1, "B"
+    for i, candidate in enumerate(('B', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB')):
+        if size < (1 << ((i + 1) * 10)):
+            divisor, suffix = (1 << (i * 10)), candidate
+            break
+    size = (float(size)/divisor) + ''
+    pos = str.find(size, ".")
+    if pos > -1:
+        size = size[:pos + 2]
+    if str.endswith(size, '.0'):
+        size = size[:-2]
+    return size + sep + suffix
+
 if __name__ is '__main__':
     print(fmt_sidx(10), fmt_sidx(1.2))
+    print(list(map(human_readable, [1, 1024.0, 1025, 1024*1024*2.3])))