"Harry Potter and the Half-Blood Prince"
Author: J.K. Rowling
Hardcover/Paperback Sold: 65 million
The sixth book in the series focuses on the split in the Wizardring world as the war with the evil Lord Voldemort begins. Harry, along with Dumbledore, feverishly tries to unmask the complex story of Tom Riddle, the boy who becomes the evil Lord.