When first published, Many Waters was marketed as the fourth book in L'Engle's "Time Quartet," which includes A Wrinkle in Time, A Wind in the Door, and A Swiftly Tilting Planet, books which involve traveling through time and space. The action of Many Waters, however, takes place several years before that of A Swiftly Tilting Planet. Not surprisingly, Many Waters shares a number of thematic concerns with these other books, including the difficulty of distinguishing between good and evil, the deceptive nature of appearances, and the importance of maintaining one's individuality and making one's own choices. Like Meg and her friends in A Wrinkle in Time, Sandy and Dennys are transported across time and space to a new world where evil beings try to seduce them into servitude. As in the earlier books, in which Meg is introduced to the songs of the stars, Dennys Murry...