I would have rated this book better, but there are a few things I feel the author got wrong. Overall, I would say this is an excellent history of the Afghan war circa 2008-2011. He delves deep into the political and diplomatic situation, as well as the philosophical debate within the military regarding counterinsurgency; all necessary discussions for a proper history. However, as a veteran of 5/2 Stryker Brigade, I saw a lot of this happen personally, and feel reality was slightly different in several instances.
He is absolutely right that the senior commanders in southern Afghanistan did not like Colonel Tunnell. He was not a fan of Petraeus-style COIN, believing instead in an antiquated, fringe philosophy of "counter-guerrilla" operations (We were dubbed, by him, a counter-guerrilla brigade, and given counter-guerilla streamers for our guidons...). However, most of the soldiers in the brigade saw this as a farce. The officers would smile and nod their heads when he lectured on his doctrine, and then would proceed to conduct actual COIN once he returned to KAF. From a company point of view (which is where the "rubber meets the road" operationally) there was little or no difference between 5/2 SBCT and any other unit in Afghanistan.
Additionally, the idea that "we lost a year" is hyperbolic and irrational. Admittedly, taking the vulnerable Stryker vehicles into the Arghandab River Valley was not a great idea, and the unit suffered great losses because of it, but that was only one battalion in a brigade which was responsible for most of southern Afghanistan. In Zabul, Spin Boldak, and eventually Helmand, we rarely had violent incidents during our deployment, and saw great gains in terms of local populace development, rooting out corruption, and building humanitarian projects. What's more, once 5/2 pulled out of the ARV, their replacement unit (4/82 ABN) suffered similarly high casualties, indicating that it was not the unit, but rather the area that was responsible for the SIGACTS.
Finally, while Colonel Tunnell may receive a great deal of the blame post hoc, the individual most despised at the time (2009-2010) was General McChrystal. McChrystal's extremely tight Rules of Engagement (no tolerance for civilian casualties) handcuffed US forces, who were afraid of being "hung out to dry" for firing artillery or attack aircraft in support of troops in contact. Subsequently, morale dropped, as soldiers developed the feeling that the commanding general would gladly sacrifice their lives in order to avoid accidentally killing Afghan civilians. The day General McChrystal was relieved was a great morale boost to troops in country.
Nevertheless, this book offered great insight into the inner working of the administration, and the roles of aid workers and the military in trying to find a winnable solution to the longest war in American history.