Two biographies of Pope Benedict XVI are available on the Amazon.com website: "Benedict XVI: An Intimate Portrait" and "Pope Benedict XVI: A Biography of Joseph Ratzinger." Both books are also avaialble in many bookstores.
"Benedict XVI: An Intimate Portrait" was written by Peter Seewald, a journalist who has known Pope Benedict XVI since 1992. The book, which was published in 2008 by Ignatius Press, is 260 pages long.
"Pope Benedict XVI: A Biography of Joseph Ratzinger" was written by John L. Allen Jr., a senior Vatican analyst for CNN and an associate editor for Crux and the Boston Globe. It was published in 2008 by Bloomsbury Academic and is 352 pages long.