The Mosquito Bowl by Buzz Bissinger is a solid book subtitled A Game of Life and Death in World War II. Bissinger chronicles how the 4th and 29th Marine Regiments of the 6th Marine Division played football against each other on Christmas Eve in 1944, with 15 of the 65 players killed while taking Okinawa in 1945.
The subsequent Battle of Okinawa was one of the bloodiest of the 20th century, with roughly 3,000 people (American and Japanese troops along with Japanese citizens) dying every day during the eighty-two-day campaign that began on April 1, 1945. The 15 killed at Okinawa was by far the largest number of American athletes to be killed in a single battle, and Bissinger notes in the preface that his father part of the Okinawa invasion, with him also in the 4th Marine Regiment.
Bissinger chronicles in the book how the loss of American life at Okinawa could have been lessened if better command decisions were made. Also, he covers how the Japanese were so willing to die, either soldiers in battle or civilians killing themselves and their families to avoid what their government told them would be torture at the hands of American troops. Additionally noted was the numerous kamikaze attacks by Japanese pilots, suicide missions against US ships.
It's a solid book and some of the fallen Marines written about were John Jackson McLaughry, David Schreiner, Tony Butkovich, Bob Bauman, and George Murphy. Of these men, the only one of them to survive the war was McLaughry, who died in 2007 at the age of 90.