Another beloved children's series will soon be over. The fifth and final of Rick Riordan's million-selling "Percy Jackson and the Olympian"...

NEW YORK — Another beloved children’s series will soon be over.

The fifth and final of Rick Riordan’s million-selling “Percy Jackson and the Olympian” books, “The Last Olympian,” is coming out May 5, 2009. The first four adventures of the 12-year-old boy descended from a Greek god include such popular stories as “The Lightning Thief” and “The Sea of Monsters.”

Riordan has another novel coming out next week, “The Maze of Bones,” the first of the highly anticipated “39 Clues” series, a planned 10-volume adventure featuring a different author for each book.

“The 39 Clues” is being released by Scholastic Inc., the U.S. publisher of the “Harry Potter” series, which concluded in 2007.