Driver's education handbooks can be picked up for free at your local DMV. They can also be downloaded online at DMV.org. Select your state and the site directs you to the appropriate manual.
Driver handbooks contain motor vehicle laws and information regarding how to obtain a driver's license. They also cover basic rules such as when to yield and how to interpret road signs, as well as important safety information. States may also include sections regarding specific driving situations motorists encounter in that state. For example, the Colorado Driver Handbook has sections covering driving in inclement weather and mountain driving.