Good book for first-time computer user?

I need to teach someone who has never used a computer how to use one. I have used computers all my life, so I don't know where to start. I thought I'd get a book. If it were Windows, I'm sure I could find a hundred books for a newbie. On a Mac, though, I'm not sure what exists out there, because most new Mac users have used Windows, whereas most new Windows users have never used a computer.

Does anyone know of a good book that teaches a first-time computer user how to use a Mac?