Bryan Peterson has been a photographer for 30 years and has been teaching photography for 20 years. In his book Understanding Exposure he gives the reader a straight forward introduction to the art of getting the exposure right.
The book is filled with illustrations and the basics of aperture, lighting and shutter speed.
This is a must have for anyone interested in learning how to improve their shots! Right now the book is available at Amazon for the reduced price of $17.13 AND, if you don't mind a used copy you can get one for just $14.00