Author and historian Michael Neiberg says that World War I is poorly understood and that "we must push for a fresh understanding of the war."
Neiberg recommends the following books:
The Sleepwalkers: How Europe Went to War in 1914, by Christopher Clark (Harper, 2013)
The Origins of World War I, edited by Richard F. Hamilton and Holger H. Herwig (Cambridge, 2003)
July, 1914: Countdown to War, by Sean McMeekin (Basic Books, 2013)
Dance of the Furies: Europe and the Outbreak of World War I, by Michael Neiberg (Belknap/Harvard, 2011)
He says these are "the best websites by far":
Mission Centenaire 14–18
A French website, with English and German translation provided.
(U.S.) National World War I Museum
The Imperial War Museum‘s site has a special section devoted studying up for the centenary
You may begin.