Marine at War was available through Scholastic Book Services and I ordered from my school at about age 10. It was a bit intense for a 10 year old boy, but it made a significant impression on me, because at age 61 I still remember nearly all of it, and I have not re-read it since then. It was written in a way that focused the action on what the individual soldier would see and experience. I recommend, and am going to re-read it now to see how it reads at this age.
I read this book when I was in middle school or high school in about 1966.
I was reminded of it today when I saw the phrase "going commando" in a cartoon, and wondered how the phrase came about, which lead North Caroline frat boys in the 1970's, Vietnam vets, and an interview with a Royal Marine, that reminded me of a bit in "Marine at War".
The author sees another marine cut a slit in the back of his pants prior to a beach landing. The other marine explained he wasn't going to give the Japanese a chance to literally "catch him with his pants down."