The Lightning Thief (Percy Jackson & the Olympians #1) by Rick Riordan

Twelve-year-old Percy Jackson has just learned that he is a demi-god, the son of a mortal and a Greek God. Percy, however, is not just the son of any Greek God, but the son of Posidon, one of the "big three"- who have promised not to have any children. As Percy discovers the truth about himself, he is cast into the middle of a battle between the Gods over a missing thunderbolt. Percy soon finds himself on a quest to retrieve the missing bolt with his friends Grover, a satyr, and Annabeth, a daughter of Athena. The group is attacked by monsters and tricked by the Gods throughout their adventure. A likeable collection of misfit characters on an exciting adventure full of mythology, mystery, and humor. The fast-paced adventure will find fans among those who enjoy the Harry Potter series, the Alex Rider adventures, and the Artemis Fowl books.