Learning through the use of guitar books is the most common and amongst the thousands of books available there are some very good ones. Using books doesn't have the highest of success rates as many simply do not have the patience to keep going when they encounter a slight problem but for those who do have a patient side it maybe an option.
Another method of learning to play the guitar is to learn by ear. This isn't for everyone but for those that can pick it up this way they will find it a lot more fun and more satisfying than learning through any other method.
Private lessons are by far the most expensive and time consuming way of learning guitar but they are also the most successful so in many respects they are the best way to learn guitar. If you have the cash and the time to dedicate then this method is highly recommended.
Finally learning to play the guitar by video is now becoming very popular. Videos are in many ways similar to books but because they are more involving and help you to keep a better focus they tend to have a higher rate of success than book.
If you have the cash and are dedicated enough to put in the time and effort then a private tutor is probably the best way to learn guitar. Apart from that I would highly recommend videos but in the end it all will boil down to what you prefer.