Crewel Lye: A Caustic Yarn (Magic of Xanth #8)

Jordan was a ghost in Castle Roogna now. Although once he had been the most valorus of knights—that is, until he was betrayed by two wily magicians and the woman he loves. Now, if he only can remember how he was killed, he'll be able to reassemble his body. And he is getting impatient....