I think the best two books on the war as a whole are:

1914-1918 by David Stevenson

The First World War by Hew Strachan

Those are the best general histories of the entire war, if you want recommendations for a specific battle or from a certain perspective I can also recommend some good choices.

If you want a work focusing on the German experience Holger Herwigs work The First World War: Germany and Austria-Hungary, 1914-1918 is where to start :)

Strachan, Stevenson and Herwig's books have already been mentioned. I'd also recommend Max Hastings's Catastrophe, Peter Hart's Great War: A Combat History of the First World War, and William Philpot's War of Attrition.

Aside from this, I'd recommend reading T. G. Otte's July Crisis, and Margaret MacMillan's War That Ended Peace, to get a different perspective than Clark's on the lead up to and outbreak of the First World War.

Apparently you're looking for general overviews, but i'd say that The Price of Glory is probably something worth looking into. Fairly brisk reading, like most of Hornes stuff, but very somber.