Everything is Fine (and Other Lies I Tell Myself) by Cathy Brett (author)

Things haven’t been going so well lately for fifteen-year-old Esther Armstrong. With her brother Max – her closest ally – absent, she’s forced to face everything alone; not least her parents’ heated quarrels. As the summer holidays stretch endlessly ahead, she yearns for a diversion. Then she finds some letters hidden in the walls of her family home, sent by a soldier to his sweetheart from the trenches of the First World War. Esther is consumed by the mystery of these lovers – not very much older than herself – and what became of them. By piecing together the jigsaw of their lives, can Esther find a way to reassemble her own and put it back together again? A moving and powerful novel which spans two eras.