PW's weekly look at print book sales based on numbers from Nielsen BookScan.

Unit Sales of Print Books by Category

Category Sept. 11, 2011 Sept. 9, 2012 % Chge Week % Chge YTD
Adult Nonfiction 6,779 4,791 -29% -17%
Adult Fiction 4,153 2,747 -34 -15
Juvenile Fiction 2,397 2,319 -3 -3
Juvenile Nonfiction 583 599 3 2

Unit Sales of Print Books by Format

Format Sept. 11, 2011 Sept. 9, 2012 % Chge Week % Chge YTD
Hardcover 3,418 2,641 -32% -8%
Trade Paperback 8,388 6,284 -25 -12
Mass Market Paperback 1,948 1,326 -32 -26
Board Books 268 305 7 0.6
Audio 106 83 -22 -11

Category segment excludes "other," which includes audio, maps, calendars, and other miscellaneous categories. Format excludes calendars, boxed sets, and other formats (i.e., maps, minibooks).
Source: Nielsen BookScan and Publishers Weekly. Nielsen BookScan's U.S. Consumer Market Panel covers approximately 75% of the print book market and continues to grow.