People have different ways of learning. (This explains why some of us had to take notes in high school, while others fared better if they just listened and watched the teacher.) You may wish to consider your learning style when making the decision whether or not to make a purchase. If you're a visual learner, you'll want photos or very good illustrations. If you rely more on written instructions, step-by-step photos will be less of a concern for you. (Those who do best when they see things demonstrated might want to look into the availability of classes, videos or DVDs, or Internet video tutorials.)
Also remember that if you're a beginner, you may benefit from a book with a strong emphasis on basic information and fundamental techniques. Books with more advanced or specialized techniques may be confusing or frustrating for a complete beginner. However, you shouldn't be afraid to try something a little more difficult. Push yourself occasionally. Just don't be too hard on yourself if you find that something isn't working out. If one project or technique is currently beyond your grasp, set that book aside for a month or two, or until you feel ready to give it another try.