Gr 5–8—This debut novel is a powerful and appealing package of skillful world-building, fantasy, suspense, mystery, and middle-school relationships. Sophie Foster, a friendless 12-year-old high school senior with a photographic memory, is plagued by the hubbub of other people's thoughts in her brain. She has always known that she is different, but her life changes profoundly when she learns that she is an elf with telepathic and other magical abilities. She is transported away from her human family forever to the elvin world, where the Lost Cities (Atlantis, Shangri-la, etc.) exist and extinct animals are thriving. As Sophie starts at her new school, her concerns about friendships, midterms, crushes, and grades in subjects such as "the Universe," "elementalism," and "alchemy" will hook readers. While navigating her new life, Sophie must solve two mysteries: First, who is setting all those magical-seeming fires in the human world? And second, who could be leaving items in her locker that repeatedly put her in serious danger? The more she learns, the more her memories return, uncovering secrets about her past. The suspenseful climax leads to a satisfying resolution, although Messenger leaves just enough threads hanging for a possible sequel. A slew of interesting and well-drawn characters, careful plotting, and just plain good storytelling will have readers racing through the pages.—Sue Giffard, Ethical Culture Fieldston School, New York City