I just indulged in a book that’s right up our alley. It’s called “Ye Gods!” by Tom Holt. If anything, it’s even funnier and more manic than Pratchett’s stuff, but the storyline actually makes more sense in a way (mainly because it isn’t as complicated). I like the fact that it takes place in real life rather than a fantasy world (I’ve been slowly moving away from pure fantasy worlds; lately they just don’t do it for me.) I’m really interested in reading his other stuff now.
Another one you might want to try is Summon the Keeper, by Tanya Huff. I particularly like this one because it’s set in Ontario (yay!) and its sequel, The Second Summoning, is set in Toronto. It’s funny in a completely different way, but it’s an incredibly good read.