Carnegie Medalist Breslin's (Whispers in the Graveyard) moving WWI novel starts slowly but ultimately packs a wallop as it chronicles the war's effects on five teens in rural Scotland. Swayed by the patriotic propaganda, 17-year-old John Malcolm, a shopkeeper's son, can't wait to fight, and his clever brother, Alex, schemes to enlist, though he's only 14. Meanwhile, upper-class Francis, an intellectual with pacifist leanings, discerns from news reports the senselessness of combat. Francis's younger sister, Charlotte, trains as a nurse and eventually tends soldiers; she and John Malcolm strike up a tentative romance. John Malcolm's twin, Maggie, somewhat precociously a feminist ("Was she unconsciously following her mother's behavior in deferring intellectual activities to the males in the house?" she asks herself), finds a new calling through war work. As the characters participate in sweeping social transformations, they also observe the warfront. Francis, corresponding with Maggie from the trenches, offers precise and disturbing details, including the "monumental madness" behind military procedures. While John Malcolm and Alex seem like stand-ins designed to represent the vast majority of soldiers, the other protagonists are forcefully depicted, allowing contemporary readers to understand the traumas of war. Ages 12-up. (Oct.)