Mint has a bunch of tweaks to make it more approachable. Apt assumes Sudo, typing passwords shows stars, little things that usually trip new users.

Meta data manager, file organiser by metadata, upload a subset to your device, sync device metadata back to your library, built-in reader, file format conversion, file editing.

It’s a whole suite really.

You already have great answers, so I’ll just drop my recommendations. LMDE if you want something more stable, and Endeavour OS if you want to go a bit more in the weeds with a rolling release.

In the end, don’t be afraid to try some for a few weeks and find one you like. One of the strength of Linux is that if you mess up, you can always reinstall,and it’s not scary since you did it once already.

Just use LMDE.

They tried. Their pirate game came out last year.

It’s like iTunes, but for books.