Really well-written, with a nice line in laconic humour (when some office-based soldier comes out on patrol and has to use his gun: It's in the job description. etc). The book crescendos with some stunning combat descriptions near the end. The thing that will stay with me most, though, is where Beattie/Gomm take the reader through what exactly an IED does to the soldier who steps on it. Talk about harrowing.
It's also one of the rare moments when Beattie's anger really shows (except several times with the cowardly Afghan National Army). I guess that's his personality, but I felt the story could have done with more of a "villain" when there was such an embarrassment of riches: the idiot planners on the British side, the ANA, the Taliban.
But then giving more of an outsider's or observer's view clearly wasn't the brief Beattie/Gomm set themselves, and there are already several good high-level, broad-brush books by the likes of Patrick Bishop and Stuart Tootal.
And by giving such an insider's view, TFH does highlight the double insanity of the whole project: a) plonking down a few soldiers in the middle of a seriously hostile well-armed country with no hope in hell of winning the war in any sense of the word that we'd recognise, and b) Beattie going back to Afghanistan at all.
Why would he? Why did he? Read it and find out.