Are there any good collections of books that are available via torrent?

They definitely exist.

I don't have links because I'm on a tablet and won't be booting up the PC I use for that today (expected power surges) or maybe even tomorrow. But they definitely are out there.

Soulseek tends to be more reliable for books in terms of easy to find publicly. Usenet is usually the default book source, but collections like you want are probably going to be easiest to find via soulseek.

Classics though, you can just get them from project Gutenberg, if they're public domain, and the real classics tend to be. That's where damn near my entire classics folder came from.

GoodReads is good for this. They have lots of curated lists and popular top 100 lists you can browse through, and you see the cover and a paragraph synopsis of each book.

Beside each book there’s a button to add it to your Want to Read list. Pick books that sound appealing until you’ve built up a decent list.

Then if you don’t feel like manually sourcing them all one at a time from LibGen or Anna’s, you can set up Readarr to automatically sync your Want to Read list and it’ll auto acquire them. If you’re already using automation apps like Sonarr and Radarr it’s exactly the same thing.

Classics you don't even need to pirate there are projects trying to make whatever is public domain available with good formatting like Standard Ebooks.

Top sci-fi maybe try searching prize winners or literary critics as terms, some people have made compilations, otherwise you can make your own compilations and create torrents.

Plenty. You should start by reading the sidebar.

Find a list of books you like, find an entry that interests you, go to anna's archive. Why overcomplicate it?

It seems like you want a curated list?