[bazookajoe]

I used to constantly have trouble with this many moons ago (lol) it always had trouble keeping non-imported books in Recent so to remedy this I've always imported books on-read/selection out of sheer habit for years now into Books > MoonReader (which is a bit annoying because that is often a double up on my device that I have to clear out after reading, but I've survived thus far).

I wish I could be more help but the best I can do is at least let you know how things are going for me on Android 9, 10, 11 and 12 (all Samsungs from cheap to flagship and one Onyx Leaf). I unchecked my "import new books automatically" setting in "Options" and also shut off any cloud connection/backup of book or read position before doing the tests.

You're on to something, but in narrow circumstances. Android 9, 11 and 12 give me no problems from either internal storage or external SD. It remembers in Recent just fine (maybe I can untick the option now after years lol).

Where I've hit issues is with my Onyx Leaf. That's on Android 10 under the hood + their own firmware. That will not remember the book in Recent, even from internal storage.
Sadly I have no other Android 10 devices left to see if it's a 10 thing or a custom firmware thing or what. As said, if it was a 10 thing or even a recent development I wouldn't have noticed as I've always just restored my old settings onto any new device and just kept it that way.

Maybe you could contact the dev and see what's what. The easy solution is to try the import books as I said but I understand space is a premium on e-readers maybe they can do a fix of some sort?