The Red: First Light gets comparisons in its reviews to Joe Haldeman's The Forever War and Robert Heinlein's Starship Troopers, both of which I read (though not the whole Forever War series) and enjoyed in different ways. The comparisons are more along the lines of how military SF progresses with its times--from glory to simple slogging to the more complex feelings we have about involvement in Iraq and Afghanistan. Instead of discoursing directly on this, Nagata tries to embody that ambiguity of modern warfare in her protagonist, James Shelley. He's an idealist who got caught up in a protest against the US government, then took the Army over a stint in jail.
One of the more uncomfortable elements of the novel is how fully the Army owns Shelley, and how he both chafes against it and accepts it. Basically it's become a part of him and there's no way out. He puts that personal transparency to use in fighting for social justice, and for trying to understand what appears to be a rogue artificial intelligence influencing people's behavior and decisions in a subtle way. He recognizes its influence more than most--the "hunches" he gets that makes a fellow soldier conclude he has a pipeline to God.
There's plenty of action and the philosophy is well distributed, so the book ends up to be a really well executed thriller that also allows you to think. I would give it four stars except that for me I couldn't really get going on it right away--took a bit to warm up. So 3 stars from me. But definitely worth reading.