Which books do you buy extra copies of on sight, especially if they're used — knowing you'll want to give them to someone else soon? Jo Walton has sparked a great discussion of book hoarding and giving over at Tor.com.
Walton says, among other things, she always snaps up extra copies of Walter Jon Williams' Aristoi and all of John M. Ford's books, because she's always giving them away. Other commenters mention Catherynne M. Valente, Pamela Dean... and Walton herself. (As for me, it's not science fiction, but I was just complaining the other day that I can't keep a copy of Small World by David Lodge on my shelf because peopel always borrow it and don't give it back, and the person I was talking to had the exact same problem with Small World. I've also loaned out/given away multiple Kushiel's Darts and keep a box of d.g.k. goldberg's Queen Of The Country Where They Sleep Till Noon to give away.)
How about you? What books do you hang onto, in order to get rid of? [Tor.com]