This. That's basically what I do too, with a small difference. First off: I usually keep all my text and non-fiction books, but I gave away most fiction. It doesn't matter if I bought it or got it from a public library. A lot of them just go back into another public library or just in front of my doorsteps for people to take em.

There are just some all time classics and fiction that struck me the right way at the right time, but I won't read most fiction a second time, so why keep em?