Patrick Hennessey's The Junior Officers' Reading Club is a lucid, witty account of all the horror, boredom and exhilaration of war. Patrick Hennessey is pretty much like any other member of Generation X: he spent the first half of the noughties reading books at university, going out, listening to house music and watching war films. He also, as an officer in the Grenadier guards, fought in some of the most violent combat the British army…