You should visit the "What should I by thread"
https://www.mobileread.com/forums/forumdisplay.php?f=123 here at MR
Then com back to check in devices (search) for Model ,=> Calibre interaction issues
Then ask
I vote for readers that support (Adobe) EPUB well (Rules out Kindles) as that format allows finer control than Mobi and many public libraries lend books compatible.
IMHO all the rest is personal taste