This is not a good method, but…
I think I’d specify an a number… let’s say, 2/3 of the books get to survive, the others will be thrown away. Then I’ll start seperating them into three groups; the ones I become immediately sure are great books, the ones I’m sure are trash, and ones I’m unsure about. Then I’ll go random: if I chose too many books as good ones, I’ll randomly take some of them out, unless I’m sure they are all great books that should stay in the library. Or start randomly adding books from the unsure pile to the ones that get to stay.
Well. Not a great method.
Timelinize… description from GitHub: Organize your photos & videos, chats & messages, location history, social media content, contacts, and more into a single cohesive timeline on your own computer where you can keep them alive forever.
There’s also Delta Chat, FairEmail and DEFINITELY LOCALSEND.