I will admit that I can see how Col. Williamson's choice of how he shared his characters inner dialog annoyed some readers. The same with the repetitive nature of some of it. But get over it, this isn't your standard historical fiction, and what the author repeatedly tries to drive home is that Vietnam wasn't your standard war. What the author does do is try to get you to see what the characters went through, the hell they endured from the enemy, their own government, and their minds.
SOG had a horrid casualty rate, and the story cycles through characters accordingly. And if you think that is a spoiler then you don't know MACVSOG. Walk with these soldiers through a country they weren't supposed to officially be in. See their thoughts and their battles. Understand what gave them PTSD.
The next time you see a Vietnam vet, tell them "Welcome home."