Lamb is my favorite Christopher Moore book. I'm not Christian, but the speculative 'biography' of Jesus that Moore creates in Lamb is a far more appealing one than the Jesus of the New Testament.
I'm currently reading Moore's newest book, Sacre Blue. It takes place in Europe during the period of the Impressionists and is a story of supernatural forces that influence the creations of Van Gogh, Manet, Monet, Pisarro, Talouse La Trec, Whistler, Renoir and other painters. It's very different than most of Moore's work, more intellectual, less slapstick, and offers a neat little art history overview of the times. It includes black and white photos of many of the paintings mentioned in the text (a color version would be much better).