My son has thoroughly enjoyed the Percy Jackson & the Olympians series of middle-grade novels. I picked up the first book, The Lightning Thief, and it was a great read. I'd recommend it to kids and adults alike. Rick Riordan (ryer-den) knows how to write a compelling, fast-moving tale with believable, complex characters... even when they happen to be the likes of Ares, god of war.
Percy Jackson is a troubled 12-year-old with ADHD and dyslexia, who discovers he is a half-blood... his father is one of the deities of ancient Greece. All those mythological creatures are real after all, having moved their residence with the expansion of Western civilization. Something is amiss at Mt. Olympus. The fate of the world is in danger, and it becomes Percy's job to keep the gods from waging World War III.
You can wait for the movie, set for release in February 2010, but I wouldn't. Something always gets lost in motion picture adaptations. Check out the book. And if you get hooked, don't worry... there are four more in the series.