I used to do 10" Kindles (normal screen android tablets infested with Amazon bloatware) that I'd 'hack' and use ReadEra for all my ebooks, and the Kindle app for the Amazon stuff.

I now have a 12" Samsung tablet, removed all bloatware, still use ReadEra (you can backup and migrate notes/etc in a new tablet). It's light, has battery for days (if you remove bloatware).

Gutenberg has thousands of books, and you can find more in 'local-themed websites' on specific languages. You can also find plenty of stuff on internet archive.

There are so many!!!/thousands of book in the "classics" and the "ancients" that will give you all the wisdom you need in life and/or the various "redbooks" (thinking of IBM rn).