The Percy Jackson and the Olympian series was written by Rick Riordan. It is based on the myths of ancient Greece, but is set in the U.S. The main character, Percy Jackson, finds out that the gods, godesses, monsters, and titans, in Greek mythology have always existed.
"This phenomenal series stayed on the New York Times Best Seller's list for a straight 124 as of November 29, 2009" Wikipedia 'Percy Jackson & the Olympians'

Book One: The Lightning Thief
Percy Jackson is an eleven-year-old boy who has ADHD and dyslexia, and lives with his loving mom and putrid stepdad, Gabe Ugliano. All seems to be going normally in his life(or at least normal on his terms) when suddenly a visit to the museum on a field trip changes everything. There he finds out that his math teacher, Mrs. Dodds, isn't even human, and in the aftermath of all of that, finds out that he isn't entirely human either. In, reality, he is a demigod, you know, half- human, half- god. I'll be careful to not explain to much more about the book, but it really is wonderful. The Lightning Thief is hard to compare to, action- packed and suspense filled, but somewhat lightly so that it is quite impossible to classify it as a thriller, or mystery. Nonetheless, it is a great book and it is number one atop my favorite books list(Along with all the other books in the Percy Jackson & the Olympians Series).

Book Two: The Sea of Monsters
When the borders of Camp Half- Blood fail, due to a mysterious poisoining of Thalia's pine tree, Percy and his friends must save Thalia, and Percy's other friend Grover Underwood, a satyr. Also, in this book Percy learns of a family member who makes him wonder if being a son of Poseidon is a honor, or a curse.This action-packed novel is just as exciting as the first, if not more. Full of strange surprises and humor along the way, The Sea of Monsters is a sensational book that will have you sitting at the tip of your seat the entire time!

Book Three: The Titan's Curse
Percy and his friends are back again in the third book of this series. The book starts as Percy, Annabeth, and Thalia (you read right Thalia) are about to recruit two half-bloods from a prep school when they are attacked by a monster. During this battle Annabeth goes missing, and not too long after,while searching for a monster(who was said could destroy Olympus) the goddess Artemis disappears as well. In a heart-breaking, funny and thrilling adventure, Thalia, Percy, Grover, and thier two Huntress friends must find the goddess, solve the mystery of the monster, and must encounter thier most dangerous challenge yet, the prophecy of the Titan's Curse.