Flags Of Our Fathers by James Bradley is excellent. Bradley's father was one of the flag raisers on Mount Suribachi, and is in the famous picture. The book deals with both the invasion and fighting on Iwo Jima, as well as the story of the three survivors in the flag raising picture (the other three were KIA) after their return home. As far as first-hand accounts of the battle, though, I'm drawing a blank at the moment.