I don't remember the books I don't like. They just find their way into the garbage (if they're despicable) and disappear...
Books that aren't that great get cleared out to the 'Sally Ann' every so often. Someone else might like them.

Unfortunately, I only remember the books I like because I reread them several times. That makes it hard to give books back to the library or my friends sometimes.
(Yes Little Hawk, you will get your books back. The question you should be asking is: when?)