That's about what I do, also garage sales and thrift stores, especially for
children's books, and Library Genesis and bookzz dot org. for electronic
books.
TPB sometimes has books too.
Don't forget that authors need to eat too. They don't get any royalties from
library books or used books so those aren't any different to them than
torrenting. John Taylor Gatto's medical fund is kind of hard to find now, but
let me know if you need me to find it for you because he's always looked the
other way when people who can't afford his books share them and I'm glad he
got my money instead of the puppetmasters of the world's second oldest
profession, the publishing industry. /vent
I don't have too many paper books, but I do need more bookshelves and a
bigger house. ;)
Just like Pentiums when XP hit EOL, some useds throw away perfectly good
paper books when they buy their swindles and crooks if you're not above
dumpster diving. I've had some amazing finds that way.
If you've got older kids or are self-educating, you can sometimes find
freebies in a box behind the campus bookstore at the end of the semester.
When I had an undergrad, the edition of her text that was used in the
classroom would be $50-$100 and the next edition down would be $.99-$3.99.
I'd grab the next edition down for her high school aged brother and me. If it
was a semester course she was taking, the teen and I could usually stretch
the next edition down to last a full year with rabbit trails through
reference books and the internet.