D-Day, June 6, 1944: The Battle for the Normandy Beaches by Stephen Ambrose
As I was reading the account of the assault on Omaha and Utah beaches, a lot of the stories reminded me of the opening scenes of Saving Private Ryan. Eventually the similarities got so great that I looked it up and, sure enough, the author of the script of SPR based those scenes on this book.
Every single vignette of horror which you see in that film really happened. If anything I think the film under-exaggerated the events unfortunately. I don't think I can watch that film the same way again.