The Last of the Doughboys is an excellent book. How fortunate that Mr. Rubin embarked on his project when he did, had he waited another year or two it may have been too late! WW1 Seems like such a long-ago war, it's been 99 years since the start of it all. But hearing from actual living veterans makes it seem much more recent and relevant. Highly recommended for any history buff.
Also Try: The Sleepwalkers: How Europe Went to War in 1914 by Christopher Clark Five Lieutenants: The Heartbreaking Story of Five Harvard Men Who Led America to Victory in World War I by James Carl Nelson July 1914: Countdown to War by Sean McMeekin