The Longest Day; by Cornelius Ryan.

It needs to be kept as a book on shelf to read more than once - one might read it, and see the film, and yet the the overwhelming character of the subject along with the exhuasting detailed research and writing leaves one submerged. One is glad to raise one's eyes and see one is not actually there, fighting for life and death for oneself as well as the human civilisation, and silently thanks those that did it before we came.