The Defense Department is attempting to buy the entire first printing - 10,000 copies - of a memoir by a controversial former Defense Intelligence Agency officer so that the book can be destroyed, according to military and other sources. "Operation Dark Heart," which was scheduled to be published this month by St. Martin's Press, recounts the adventures and frustrations of an Army reservist, Lt. Col. Anthony Shaffer, who served in Afghanistan in 2003, a moment when the attention of Washington and the military had shifted to Iraq.