Your  favorite nonfiction book last year was not even a 2009 title.  Greg Mortenson’s Three Cups of Tea,  about the  climber who built  schools in Pakistan, went out 20 times in 2009. His new book,  Stones for Schools, is much anticipated.    Readers also turned to books on decision making (How we Decide),  the food industry (Why We Eat, Food Matters), and nature studies (Sand , The Beast in the Garden).  Favorite biographies included Losing Mum and Pup, Christopher Buckley’s affectionate/scathing memoir of his celebrated parents and Not Becoming My Mother,  a warm appreciation by food writer Ruth Reichl.  Politics and History, though a popular subject area (260 loans) rated no one top title.  The most popular of these was Horse Soldiers, a story about covert operations in Afghanistan.