Reviewed by Sue GaisfordSERPENT’S TAIL, 572pp, £25 Tablet bookshop price £22.50 Tel 01420 592974 Every week, of every year, literary editors find among the haul of new books at least two about the world wars of the last century. In this centenary year the proportion has dramatically increased. This book, however, is different. If you want to know what the Great War of 1914-18 was really like, you need read no other. Pete Ayrton has collected the best prose about that war. Mostly, he uses fiction, but fiction and autobiography can be very close, and every extract rings with authenticity. He includes writers from 20 countries, from the Western to the Eastern front, from the Balkans to the sea and, in telling little essays at the end of each, he puts them into their wider