Rick Riordan is the author of the Percy Jackson ... The 39 Clues can't rank higher in Riordan's list of book series because ...

Rick Riordan, read by Robbie Daymond. Listening Library, , unabridged, 9 CDs, 10.5 hrs., $50 ISBN 978-0-451-48519-9 In this book, the first in Riordan’s Trials of Apollo series (a spin-off of ...