This book is probably responsible for more people getting into homebrewing than any other book. It's the gateway through which many of the great micro-breweries' founders got their start in brewing.
Charlie has a wonderful casual writing style which is easy to read while not dumbing down the material. While nominally a technical guide, it's also entertaining and extolls the spiritual virtues of great beer, beer with soul.
Some other books may be more technically accurate or up-to-date on specifics of technique, but they just aren't as enjoyable.

If you like beer and brew beer, have wanted to brew beer, you should own this book. Papazian's infectious passion for beer and his straight-forward approach are wonderful.