I have a great fondness for second-hand books and get a kick from knowing that they've been on someone else's shelves before. It's even better when there is a clue about the identity and character of that owner in the form of an inscription on the inside cover (or as in one instance, a letter between the pages).
Came across a great page of classic book inscriptions from the Deuce of Clubs website (discovered via Mountain Murmurs).
Find out why you shouldn't ask Darth Vader to sign your book, how to trick a US vice-president into autographing a book that isn't his, and how to throw your wife off the scent if she thinks you might be getting ... restless.
And then there's the brilliant bookplate (left) found in a book about reincarnation. (If you don't get the joke, you clearly need more coffee!)
And then this just for Sharanya, who asked some time ago whether she could copyright the title of her novel ...