Light backstory in regards to my starting to read this series: I'd been reading The Passage by Justin Cronin (fantastic book, by the way) and it scared the dickens out of me, such that I found it impossible to read in the evening before bed for fear of nightmares and such. (I felt better about this when the person who suggested the book also got nightmares from reading it.) So my mother suggested Janet Evanovich's Stephanie Plum books for evening reading.

The books aren't fantastic, but they're short, entertaining, and funny. Quite like the Sookie Stackhouse series, but far less annoying and far more amusing. The characters are hilarious and quite believable. And as you can see, they go fast. You can easily read one, or at least some of the earlier books, in a day. Your local used bookstore is almost certain to have these in mass market paperback, which I have resorted to when I wasn't able to find the copies my parents own.