This is the book by E.B. Sledge, "Sledgehammer", about his experiences as a Marine mortarman on Peleliu and Okinawa during WWII. If you saw "The War" on PBS he was featured in it.
Great book, absolutely great. He doesn't try to impress the reader with overly lurid adjectives about the hell he saw. What I mean is, you don't get the impression like you get watching some modern special effects filled movie. He doesn't resort to tons of profanity or passages of "flying lead smashing bones and flesh!!". Rather, his simple and very literate prose bring home the horror, fatigue and inhumanity with far more force.
One example - he was stuck in a muddy fighting hole on a ridge in Okinawa for several days where he had to look out on the decomposing corpse of a new replacement (among many, many other maggot infested rotting corpses) seemingly staring back into his face. His straight forward description of the body and the situation just floored me. That was one incident out of dozens.
The book is well researched and his accounts from ground level are interspersed with details of the strategy and larger movement of units during the two campaigns.
After reading this I watched a bunch of combat footage on youtube about the exact same places - The Horseshoe, taking Negesebus and crossing the airfield on Peleliu and the fighting and miserable rainy conditions on Okinawa. Particularly in some footage of taking Negesebus island you wonder if you're watching the very amtrac that Sledgehammer was riding in during the attack.
http://www.youtube.com/watch?v=SET-SF0gZGk&mode=related&search=
