Symbolism, Imagery, Allegory
When Kevin is sick, Eva reads him Robin Hood and His Merry Men. And Kevin likes it. He really likes it. Eva has no idea why Kevin likes it—but the book sure serves as a grim foreshadowing of Kevin's archery talents. "Kevin Khatchadourian could put an arrow through an apple—or an ear—from fifty meters" (27.3). And he uses his sharpshooting skills to, you know, kill his classmates.
But is there a deeper connection between Kevin and this book? Does he somehow identify with Robin Hood? It isn't like Kevin is a person who is stealing from the rich and giving to the poor. But what if we don't think about money, exactly? Kevin does feel like an outsider. Is he taking something from other people and giving it to his mother? Like general human emotion, perhaps? Or, like Eva, are we just reading too much into it?
Whatever the reason, Eva keeps a copy of this on the bookshelf in her spare bedroom, the room Kevin will take when he gets out of jail. The book is both a comfort to Eva, this one thing she knows her son likes, and an olive branch to extend when he comes back into her life.