I read the first book a couple years ago. It's not terrible but the author is kind of shameless in how he jacks every beat from Potter. Instead of Hogwarts there is Camp Half-Blood, there's a Ron, Hermione, Snape, and Voldemort. It gets ridiculous. I hope the later books are different.
http://www.moviefone.com/movie/percy-jackson-and-the-olympians-the/32797/hd/480