Book seven of Jeff Kinney's Diary of a Wimpy Kid series, The Third Wheel, has passed the million mark in physical copies sold, according to Nielsen BookScan. The title needed only five weeks (it was published by Abrams/Amulet on November 13) to cross the milestone, and it has been BookScan's overall #1 bestseller every week since publication. For the week ending December 16, sales of The Third Wheel actually increased 11% over the week before, thanks in part to an Amazon lightning sale of the book for $1.99 on December 14.

With only a few days left in the calendar year, the book will be the last to pass 1 million copies sold in 2012, and it will end the year as the #6 bestselling book of the year, placing behind only the Fifty Shades trilogy, Catching Fire, and Mockingjay. Fifty Shades of Grey, the #1 title, has sold 6.2 million copies; Mockingjay, the #5 title, has sold 2.2 million copies.

The Third Wheel's BookScan sales number of 1.1 million is lower than its real number, as BookScan accounts for roughly 75% of total physical book sales in the U.S.