Some yardage books are quite fancy, printed on high-stock, glossy paper with full-color illustrations. Other are more basic, with black-and-white line drawings.
All serve the same purpose: to help the golfer plan his way around the golf course.
The primary purpose of the yardage book is, no surprise, to provide the golfer with yardages. On Hole No. 1, the illustration might show a hole that doglegs slightly left, that has fairway bunkers at 180 and 240 yards off the tee, that has a small pond in the rough right of the fairway at 200 yards. It might show the golfer that the distance from a certain tree to the putting green is 140 yards, and so on. The shape of the hole, the hazards on the hole, and important landmarks are all noted, and the golfer is provided with distances (to objects from the tee, and to the green from objects).
Recreational golfers are most likely to encounter yardage books at higher-end golf courses - resorts and higher-priced daily fee courses. Sometimes a yardage book is complimentary and included in the green fee; more often, yardage books are sold separately and the golfer has the option to buy or not buy.