The Spellman Files by Lisa Lutz
I haven't enjoyed a family this much since I met Janet Evanovich's Plums. The Spellmans are wacky, dangerously brilliant, and deceptively normal when it's all said and done. I couldn't wait to get my hands on this one after reading several reviews. I hope Lisa Lutz is locked in a room and writing furiously because I want more Spellmans! These are the kind of characters that get into your head and inhabit that shadow universe where you sometimes forget they aren't real. I'm not sure I'd want to be part of the family, but just being in the orbit of the Spellmans seems to be adventure enough.
If you haven't already read this, go buy or borrow it right now. You won't regret it!