The Lightning Thief by Rick Riordan
Also by this author:
The Sea of Monsters
This book is recommended for advanced readers in fourth grade and up
(includes elements of Fantasy with a twist of Realistic Fiction)
Readers of Greek mythology and reluctant readers alike will enjoy the adventures of Percy Jackson, a modern New Yorker who battles a Minotaur before attending a special camp for "half-blooded" children of Greek gods.
Fast-paced action and clever retorts will appeal to many readers, and fans of Greek myths will enjoy connecting well-known characters to this book's modern counterparts. This is one of the most compelling, can't-put-it-down kind of books in this genre. The book includes some violence, such as swordplay between humans and with monsters. Characters make references and occasionally pray to various ancient Greek gods and demi-gods during the book.