As the United States commemorates the centennial of the country's active engagement in World War I, a new book tells the larger story of that conflict through the individual stories of its most valiant and emblematic soldiers.   For the first time, bestselling author Patrick K. O'Donnell provides a narrative history of the Tomb of the Unknown Soldier and the battlefield exploits of the hand-selected Body Bearers who laid him to rest in THE UNKNOWNS:  The Untold Story of America's Unknown Soldier and WWI's Most Decorated Heroes Who Brought Him Home.   Patrick will also be signing his book in the Museum Store following the lecture.