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

Unit Sales of Print Books by Category

Category Sept. 18, 2011 Sept. 16, 2012 % Chge Week % Chge YTD
Adult Nonfiction 5,563 4,520 -19% -18%
Adult Fiction 3,563 2,608 -27 -16
Juvenile Fiction 2,254 2,189 -3 -3
Juvenile Nonfiction 544 589 8 3

Unit Sales of Print Books by Format

Format Sept. 18, 2011 Sept. 16, 2012 % Chge Week % Chge YTD
Hardcover 3,080 2,636 -14% -9%
Trade Paperback 7,012 5,891 -16 -12
Mass Market Paperback 1,668 1,157 -31 -26
Board Books 294 306 4 0.7
Audio 93 86 -8 -10

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.