He has written I believe 7 mythology books for kids. Not sure.
It has indeed been 7. In the Percy Jackson and the Olypians series; The Lightning Theif, The Sea of Monsters, The Titans Curse, The Battle of the Labyrinth and The Last Olympian. In The Heroes of Olympus series there is the first book, The Lost Hero, and there is going to be The Son of Neptune this fall. Then in The Kane Chronicles there is The Red Pyramid and there is going to be The Throne of Fire this....May I beleive, or really close to that. So 7 and 9 by the end of this year. Did this help?