Loveable characters and a story that's quirky and unusual in all the right ways. If you want something that's funny but not vain, and something that's exciting but not (really) dark, this is the perfect choice.

(Should it be relevant: I watched the show too, after reading. The show and the book really are very similar, it's quite impressive, I prefer the book only by a tiny margin for a tiny detail, but both are very valid choices.)