The Magic Tree House series by Mary Pope Osborne stands at 35 books and counting. Among children ages 5 to 9, Osborne has earned a cult-like popularity that rivals J.K. Rowling, says the Raleigh Independent Weekly.

The Hank Zipzer books, featuring the World's Greatest Underachiever, by Henry Winkler and Lin Oliver.

The Spiderwick Chronicles by Holly Black and Tony DiTerlizzi.

Third Grade Detectives by George E. Stanley.

The My Weird School series by Dan Gutman and Jim Paillot.

The Boxcar Children, a series written by Gertrude Chandler Warner in the 1942 using only the 500 most common words in the English language to create an easy-to-read chapter book.

Ramona the Pest by Beverly Cleary, who turned 90 this year. Ramona is being made into a movie, but Cleary promises she won't turn into a plastic fast-food toy.

Nate the Great mysteries by Marjorie Weinman Sharmat.

Cam Jansen mysteries by David A. Adler.