Janet Evanovich's Plum series has to be some funniest novels ever written! I just started re-reading them waiting for the next one to come out on June 19th! I can't wait till the 19th! I'd read them all before and I was still roll on the floor laughing! Laughing till tears rolled down my face. Just the character descriptions in these books makes you laugh.
Do yourself a favor and Read One for the Money. I know you'll be hooked! Here's the web site http://www.evanovich.com/