epub files not working

Books uploaded to the Apple Book Store most likely were created by Apple's iBooks Author, Pages, Vellum, or another third-party tool using the specific formatting for the Apple Book store.

Although these are using a standard EPUB3 container format, the actual HTML and CSS3 internal styling that allows the EPUB to be readable have Apple-specific coding in them that dictate how to appear when opened in Apple's Books application.

And Books generated for Amazon's Kindle by Kindle specific generators use Amazon's own DRM protection, much less HTML and CSS3 features to make their EPUB3 books only usable on Kindle readers, not Apple's Books application. The older Amazon Kindle books were based on a different spec: MOBI instead of EPUB[2,3].

So there remains no universal utilitarian platform agnostic E-book document standard other than PDF as each company puts their own unique spin on the EPUB3 contents.

ok. well, I have now tested over half my books, none of which came from the apple bookstore, and all the ones tested opened and worked in the books app in epub format.

I'm not sure if this will help.

but you can set up a new user and test your books in the new account. please see Set up users, guests, and groups on Mac - Apple Support.

and I would also try and start your Mac into safe mode. then you can test while still in safe mode. sometimes a safe boot followed by a normal boot will clear up small anomalies. please see How to use safe mode on your Mac - Apple Support.

I have just downloaded epub files from the web and opened them in Books today, so the idea that Apple is restricting Books to open only those from its own store is not correct.

Are these files perhaps in an external drive? I haven’t tried it but maybe it’s a permissions issue? You have not yet said what exactly happens when you try to open an epub besides “it doesn’t work”… does it give an error message, and which one, specifically? If possible post a screenshot of that error?

I have tried several epub files from project Gutenberg and also from archive.org, and they ALL opened perfectly. I tried them both on an Intel and an M1 Max Mac, all macs running Ventura. I have yet to find any epub that fails to open.

Perhaps you can tell us an example of an epub that doesn't work, for you, so we can test. A free one, of course, as I am not going to buy an ebook just for testing.

Just deciding on your own that this is a deliberate underhand ploy is not going to help you use your epub files, and just isn't true.

Of course, Books is supposed to open epub files, I forgot about that. Indeed, the books downloaded from the Books store are in epub format!

And the ones I tried, including some downloaded just now, it DID open... what exactly happens in your mac when you try to open an epub file?

sorry, I cannot replicate your issue. I have tested this with several of my epub books within Apple Books. I have no issue opening any of the ones I tried, and am sure I would have no issues with the other couple hundred epub books.

i'm thinking you should download and run the free version of EtreCheck so we can see if you have some software installed that is causing your issue. make sure you give "full disk access" to etrecheck. Learn how to use it by reading Using EtreCheck. if you need help interpreting the report, you can see how to post the report here by reading How to use the Add Text Feature When Posting Large Amounts of Text, i.e. an Etrecheck Report. and it automatically obscures sensitive things (like serial numbers) so you don't have to worry about sharing the report here.

Perhaps you just need to install an application to read epub documents... there are many in the App Store, some of them free.