This is one of the books that got me started down the road of photography (or should I say, more than randomly pointing and shooting).  Bryan Peterson’s Understanding Exposure covers a lot of ground for the beginner/intermediate photographer, explaining the different combinations that make up the photographic “triangle” – aperture, shutter speed and ISO.  While there are  many correct exposures, there may be one creatively correct exposure.

It is very easy to understand and touches on many different situations and subjects.  I would highly recommend giving it a read, and have read it more than once myself.  You can find it on Amazon, and it looks like a new edition is coming out soon (Understanding Exposure, 3rd Edition: How to Shoot Great Photographs with Any Camera).