Booof. This book is the extremely first person account of doing a tour duty in Afghanistan as an army grunt. It doesn't necessarily tell you anything you didn't know about the war there, but it does present the things that you know at a very close level of detail and with tons of lived experience.
Another way of describing the book and its author would be: "what if every aspect of my life and all of my decisions were the complete opposite?" So there's a whole bunch of switches that get flipped to their opposite: dirt, violence, personal courage, sleep deprivation, weight lifting, food, temperature, drinking, personal hygiene, sanitation, etc. etc. Suffice to say that I'm happy with my choices. :D The stories do make for good reading though. The start of the book and the end of the book are a bit rough, but the middle 80% which describes living and soldiering in Afghanistan is compelling and interesting.
A third (and hopefully final) way of describing the book would be to say that the book is about the difference between theory and reality, between abstractions on a military map or in an opinion piece and what is actually happening in the world. So you have mine-detectors, but they don't actually detect mines. You have Afghan army units, but they absolutely will not fight. You have police, but they will refuse to act in even the most basic ways (e.g. drive this wounded civilian to a hospital) unless bribed. You have provincial governors, but they are arguably Taliban. You have reconstruction projects, that no ones uses and are abandoned and are eventually turned into forts by insurgents, and then bombed by coalition air strikes and turned back into rubble in some sort of weird cycle of life. It's just one thing after another that exists only on paper or only in the dream-castles built up within documents and speeches. It's theory crafting. It's what happens when you try and take Western idealism and try to force it on a Vancian society.
Afterward 1: The author also does podcasting, which is where I first heard about him. One of their better out-takes is here (tons of cursing, NSFW, Trigger Warning: Academic PTSD).
Afterward 2: After a long percolation, there actually is one other thing the book taught me/made me realize, which is just how much human damage gets hidden from the casaulty figures by advances in medical treatment. Out of the ~20 soldiers the author was grouped with, ~100% of them had some sort of fairly serious injury from their time in Afghanistan. On the low end, these are things like ankle injuries or chronic lower back pain, which never get officially recorded but will stay with a person and crap up the rest of their life in minor daily ways. Ramping up a bit, there's a host of psychological issues of various levels of severity, and then beyond that the actual concussions, brain damage, and serious wounds caused by combat. In the US Civil War, about half of his group would have been dead from the wounds they suffered, which we would rightly recognize as a horrific casaulty rate, enough to destroy a unit. But thanks to advances in first aid, transport, and surgery, only a few of his unit were listed as injured and none of them actually died. And when you just look at the basic casualty figures, it hides just how much his group (and one assumes other groups) went through and were hurt.