I used to also collect books (as trophies?), but then I was moving a bunch and traveling and they would just sit in a rented storage unit anyway, so I gave lot of those away.

I have a folder with digital copies of all books I read (multiple of them "stolen" from zlib and Anna's Archive, but imo fair game since I had those). I have this folder synced across devices with syncthing. I also have a digital note with the list of the books and when I finished them (Goodreads is a good option for this, but I like self hosted)