A boy with a backwards heart

[Koontzfan]

The book I am searching for is about a girl (I believe she is in high school) and a boy who teaches her how to travel into higher dimensions.

I don't remember too many specifics from the story line, but something that stands out in my memory is a dialogue between the boy and the girl about what we as three-dimensional beings would look like to two-dimensional beings; for example, what would a two-dimensional being, living on the surface of a pool, perceive of us as we dove into the water?

Other than that, I seem to remember that somehow the girl noticed, early in the story, that the boy's heart was on the wrong side of his chest, and that he explained that it was as a result of re-entering our dimension from the wrong direction, or something like that.

I appreciate the help.

 

[erinsbooks]

I think it's a Will Sleator book. Does this sound right?

The Boy Who Reversed Himself

William Sleater 1986

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.