Ebook reader

Perhaps having two apps onscreen simultaneously would be the easiest solution?
From Google:
“Use two apps at the same time with Split View
1). Open an app.
2). Swipe up from the bottom of the screen to open the Dock.
3). On the Dock, touch and hold the second app that you want to open, then drag it off the dock to the left or right edge of the screen.”



Try https://ebook.chessvision.ai/ it does exactly what you described for PDF books
I haven’t been able to install e+chess books in the US for some reason

I just checked and found that all of the books have been removed from the app’s bookstore. Perhaps the company went out of business.
Why not try some of the chessable stuff? https://www.chessable.com/the-checkmate-patterns-manual/course/17841/ or https://www.chessable.com/course/40115

I had actually started a thread in @chessdotcom feature request re the split view in iPad. Add to that chess.com iOS app doesn't even have an analyze position option.
Had posted in another thread (link below) how one can use the kindle ebook reader in Split view and run a free app in the next window.
(Copy/Pasting from that thread below.)
For those reading Kindle books on an iPad, one feature they can make use of is the Split View in iPad. One can run two apps next to one another.
Most Chess apps don’t support this feature and in most cases, the kindle app opens as an floating app rather than in split mode.
The best option for Split view is a free app which is a chess.com rival, so I won’t post screenshots here. The app nicely resizes itself in a split screen mode, making it possible to view the game in interactive mode, engine analysis and even edit positions on the board. (Hint: Name starts with L)

Another option is "Analyze This" app. It does run in Split view mode but resizing is not perfect. Position setup is difficult as well. Posting a screenshot with kindle and Analyze This running in a split view.

I've been using chessvision.ai and their ebook reader, it's pretty damn good and the most cost efficient way to go about things. https://ebook.chessvision.ai

And, after one of Asim Pereira's apps has already been mentioned, have a look at his solid Chess Book Study:
https://play.google.com/store/apps/details?id=com.pereira.booknboard
It needs a bigger screen but works with a lot of formats.
Good chess,
superlychee

I’m gonna stick with print books if I lose another purchase because the app is no longer available.
You won't lose any purchase in our reader https://ebook.chessvision.ai/ because we don't sell any books, you just upload the books you have