Amazon posted a link for a Darth Maul Bio hardcover by Ryder Windham (Scholastic) for January 1, 2012 (meaning the book will probably appear at the end of December 2011). Amazon's listing mentions that the book will have 224 pages. Here's the link.
After The Rise and Fall of Darth Vader (September 2007), The Life and Legend of Obi-Wan Kenobi (August 2008), and A New Hope: The Life of Luke Skywalker (August 2009), this appears to be the fourth entry in the series of slipcased bio-books by Ryder Windham for Scholastic.