Bristol Palin, the single mom and reality TV star whose mother is toying with a run for the White House, will sign copies of her memoir at the Mall of America, officials from the Bloomington shopping center said Monday. Palin, 20, will appear from 6 to 8 p.m. June 29 at the mall's rotunda, bringing her back to the Twin Cites, where her family burst onto the national scene when her mother, Sarah Palin, accepted the No. 2 spot on the Republican Party's presidential ticket during the 2008 national convention in St. Paul. Bristol Palin's book, "Not Afraid of Life:...