Mixed feelings on this one-- Christopher Moore can make me howl with laughter, but this one combined so many elements (previous characters, CM books, several Shakespearian plays, several other literary and dramatic works, and an extreme sense of the absurd) that it took me a while to find the rhythm. I actually put it aside for a few days and then started over.
Previous characters: Pocket the fool, his assistant Drool, and the monkey Jeff (also the ghost of Cordelia, last seen romping happily with Pocket in Moore's <i>Fool</i>.
Previous books: See above
Shakespearian plays: Merchant of Venice, Othello, with throwbacks to Lear
As to the others you'll have to discover for yourself.
But forget everything you know from your high school/uni English classes. This Venice has sea serpents in it. And it's a wild ride.