The Boy Who Reversed Himself by William Sleator
Synopsis: 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.
Published: 1986 | ISBN: 978-0140389654
Mini-bio: William Warner Sleator III, known as William Sleator, was an American science fiction author who wrote primarily young adult novels but also wrote for younger readers. Wikipedia
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Paperback Edition: The Boy Who Reversed Himself