I picked up The Lightning Thief on Playaway at the library because I liked the cover and the really really short blurb on the back sounded fun.
It totally sucked me in. It was greatly helped by the fact that I loved the narrator, but it was just fun. It didn't expect to be taken seriously. All the characters, especially the minor ones, are realistic and worth caring about. I just loved it.
I was totally shocked to see a preview for a Percy Jackson & the Olympians MOVIE when we went to see HP. Turns out there's like a whole series and it's been out for a while and they've been best sellers? I pretty much live in a cave.
They're not The Great American Novel but Rick Riordan knows that. These books are often laugh-out-loud funny and I love the blending of Greek mythology with modern day situations. Great reading for a Summer afternoon.
Summaries on Goodreads here and here