This is an excellent book for those who are first starting off in the world of homebrew. It covers the absolute basics from what equipment to purchase through to more complex matters like formulas for calculating the differences in hop bitterness values.
The book includes brewing from kits, the extract brewing method and explores the more advanced full mash brewing. This book is up to date with techniques and ingredients and in written in an easy to understand way. It also has a large range of recipes for both extract and full mash beers.
Once you have mastered the recipes and techniques in this book I'd recommend How to Brew: Everything You Need to Know to Brew Beer Right for the First Time
for intermediate to advanced brewers. This covers a lot more of the chemistry behind beers and is truly a great reference guide.