* Percy Jackson & the Olympians series: 5 books
* Heroes of Olympus series: 5 books
* Trials of Apollo series: 5 books
* Magnus Chase and the Gods of Asgard series: 3 books
* Kane Chronicles series: 3 books
* Percy Jackson & the Olympians: The Lightning Thief (graphic novel): 1 book
* Other books: Various standalone novels, short stories, and graphic novels
In total, Rick Riordan has written over 20 books.
His books are incredibly popular, with millions of copies sold worldwide. They've been translated into dozens of languages and adapted for film, television, and theatre.