Twelve year old Percy Jackson has some problems. He is dyslexic and has ADHD to the max. As a result, he gets kicked out of every school in which his mother enrolls him. His stepfather is a jerk, and he doesn't know his real dad. As the book opens, Percy is on a field trip to the Met with his fellow classmates. Just a typical, boring field trip until one of the teachers turns into a Fury and tries to rip him in half. Percy realizes that dyslexia and ADHD are the least of his problems, when he discovers that he is a demigod -- half man, half god -- and that he is caught in the middle of a war that is threatening to tear the world apart, quite literally.
The Lightning Thief is a quest story set in modern times. The setting moves from New York City to St. Louis to L.A., as Percy works his way toward the West Coast, where the entrance to the Underworld is located. He is helped along on his quest by Grover, a satyr, and Annabeth, another child demigod.
The Lightning Thief is the first book in a five-part series, called Percy Jackson & the Olympians. Four books have been released. If you liked the Harry Potter series you will probably like this book. It is written for the same audience. Riordan even cribs a little from the Potter series. The protagonist in the book is helped by two best friends, a boy and girl. There is mystery surrounding his past. And the Greek-god world exists alongside the mortal world, hidden in plain sight.
I liked how Riordan brought the Greek gods into modern times, updating them, but not fundamentally changing who they are. I am sure he fudges a little on some of the details to make things fit his story, but I don't know enough about Greek mythology to notice.