Hindenburg and Ludendorlf

I just finished Dupuy's brief book on the collaboration between Hindenburg and Ludendorff on both the Eastern and Western Fronts. What other books are recommended?

I recently read The Guns of August, which talked about both of them, briefly, but as the book mostly focused on the actions of August 1914 with a focus on the armies, not the generals, it didn't go into them much.

>2 Karlstar: I read Barbara's Tuchman's book some years ago. Its a very good synopsis of the immediate causes of the Great War.