Apple Books Shows "Book Content Unavailable" or Nothing

[Rand Brittain]

I'm working on an EPUB version of a friend's book, and I'm finding it impossible to get the EPUB to load on Apple devices, even though it passes every form of validation I'm familiar with, including EPUBCheck, Calibre's validator, and Sigil's validator.

On one tester's device, it gives a message saying "Book content unavailable"; on my own devices, it shows every chapter in the book as a blank page.

Has anybody ever seen this before?

[DNSB]

I think you might want to scramble the epub and attach it to a message here. Otherwise all we can do is to supply wild guesses.

[Rand Brittain]

Fair enough, and it was easy enough to do.

[Rand Brittain]

This is honestly not dissimilar to a problem I had several years ago, where I was able to fix the EPUB by importing into iTunes for PC and getting it to add an iTunes metadata file to the folder, but... apparently iTunes for PC doesn't have that function anymore? Seriously?

[KevinH]

Apple Books apps uses its own caching mechanism. The first time you add a book, it is unzipped and stored away and a cache of the cover and metadata is made.

So if you tried opening an early version of the epub (incomplete) in some way, the cache will get generated from that and not updated.

The solution is to delete all copies of the epub from Apple's Books so that its caches are emptied, then add a known good copy.

Seeing just blank pages sounds like a missing font or broken css issue. Does your epub embed a body font?

Have you properly created and added the file:
META-INF/com.apple.ibooks.display-options.xml

This is the Apple non-standard epub additional file. See our Mobileread Wiki for details:

Embedded fonts will not be used by iBooks unless a special file is included in the ePub with special content. The file is: META-INF/com.apple.ibooks.display-options.xml and must contain:
<?xml version="1.0" encoding="UTF-8"?>
<display_options>
<platform name="*">
<option name="specified-fonts">true</option>
</platform>
</display_options>

[KevinH]

Also, There are many other good epub readers for iOS, many free. Have you tried any of them?

[DNSB]

For what it may be worth, when I look at the ePub with 7Zip, I see the com.apple.ibooks.display-options.xml file in the META-INF directory. The contents of that file are:

<?xml version='1.0' encoding='utf-8'?>
<display_options>
  <platform name="*">
    <option name="specified-fonts">true</option>
  </platform>
</display_options>

I think this is correct location and structure for allowing iBooks/Books to display embedded fonts.

One possibility for testing is to remove that file since the scrambled epub does not have any embedded fonts and see if the ePub then displays correctly.

[Rand Brittain]

The ePub does have embedded fonts, and they aren't optional since they include some special characters; it looks like the scrambling process just removes them.

[Rand Brittain]

Originally Posted by KevinH

The solution is to delete all copies of the epub from Apple's Books so that its caches are emptied, then add a known good copy.

Is there a standard way to do this? Just deleting it from iBooks wasn't enough in the past; that was the problem I had to import it into iTunes and back out to fix in the past, but I'm not able to do that anymore.

[KevinH]

In the old days you just fired up iBooks and deleted it from your Library shelf. Then exited out of iBooks. Then fired up iBooks and manually added the new version of the epub.

If in the new Books app that no longer works, then I would open Calibre or Sigil to edit the epub's opf and change the unique id pointed to in the opf package tag with a newly generated uuid.

This would/should force a new cache entry.

[KevinH]

FWIW, in Books on macOS, I had no issues loading or seeing the scrambled pages in what you posted for us to test with.

So whatever issues you are having with this epub in Books, your scrambled version is showing up fine in Books app on macOS.

It also showed up just fine in Sigil. There are missing xml headers and doctypes based on the strictest interpretation of the epub3 spec but those are autofixed by Sigil on load and are not causing any issues.

I also tested it with iOS Books.app and could also see the text just fine.

[Rand Brittain]

The last time I changed the UUID, it didn't help, but this time, the EPUB loaded. Maybe the difference was deleting the cloud copy from Apple Cloud Drive? I dunno. Either way, it works now, so thanks!