Can anyone recommend a good one? One that covered the military, as opposed to political, aspect would be the most welcome.
The Anarch is to the Anarchist what the Monarch is to the Monarchist. -Ernst Jünger
One book that's handy for starting researching and to always have available when studying the subject it's The World War I Resource Book by Philip Haythornwaite. It just covers the basis but it covers them all, from brief summaries of what went on the various fronts, to how each army was organized, to the various propganda machines etc.
There are two books that cover the whole of the war: The Real War 1914-1918 by Basil Liddell Hart and The First World War by Martin Gilbert. Neither has aged terribly well but they are the only affordable and comprehensive military history books covering all the fronts.
The same cannot be said about The Price of Glory by Alistair Horne. Despite having been written decades ago, it's still the best book about Verdun and one of the finest, if not the finest, WWI book. The good part about this book is it was the first to fully detail Petain's plan for Verdun, which would have probably ended the war a full year in advance.
On the Origins of War: And the Preservation of Peace
I paid four bucks for the HB. Goes over the military maneuvers of leading to WWI, WWII, Peloponnesian War, Hannibal's Second War, and the Cuban Missile Crisis. if you're looking for the actual military maneuvers of the war I don't know.
Have either of you read Hans Delbruck or have anything to say about him?
Yes, I own the Delbruck series. In my opinion his books are masterpieces because they revolutionized how military history is researched and written. His works on Ancient Greek and Rome were a pivotal point in modern historiography.
His WWI work is a posteriori rationalization of the thesis he held before the war started, namely that no matter how well geared for war Imperial Prussia was, it was bound to be defeated if she squandered her forces on more than one theater at a time. Delbruck didn't adhere to the Schlieffen Doctrine, which dictated a quick, decisive blow on France followed by a similar move on Russia, whose armies were to be left advancing in Poland and then defeated using internal lines movement to transfer the troops freed by victory on the Western front. Delbruck rightly rationalized it was wrong to assume the Schlieffen Doctrine would have worked exactly as planned, and facts seem to confirm his view: Gallieni stopped Von Kluk on the Marne and Von Moltke the Younger caved in to pleas to transfer troops to Poland to keep the Russians in check. In Delbruck's opinion the war was lost by Prussia even before the first shot was fired.