The Boy Who Reversed Himself

When Laura finds her homework in her locker with its writing reversed, she's baffled, until she learns an unbelievable secret: her weird neighbor, Omar, has the ability to travel to the fourth dimension. Laura forces him to take her there, and then, a novice in "four-space", she goes there on her own. There's only one problem: she doesn't know how to get back. "A cerebral science-fiction thriller, cunningly constructed to keep the reader involved until the last pages." -The Horn Book