Toby's Room by Pat Barker

Toby has always protected his sister, Elinor, their bond closer than they can acknowledge. Then comes war, and in 1917 on a French battlefield Toby is reported 'Missing, Believed Killed'. Elinor, an artist now involved in helping surgeons reconstruct the faces of injured soldiers, is determined to find out what happened and writes to the horrifically wounded Kit Neville, the last man to see Toby alive. But Neville is in hospital, himself damaged beyond recognition, and he will not talk - until Elinor asks fellow soldier and her former lover Paul Tarrant for help. But are some truths better left concealed?