First off, it should be pointed out that this book is concerned with creating recipes. It is not an introduction to home brewing and doesn't have any information on technique. If you're looking for an introduction to brewing, or an introduction to full mash brewing then John Palmer's book, How to Brew: Everything You Need to Know to Brew Beer Right for the First Time
, is excellent, and also free on the web.
This book is split in to two parts. The first part, which accounts for about a third of the book deals with brewing calculations. Things like how to estimate your mash efficiency, hitting your target OG, and calculations for minerals additions to your water.
This section is quite good. Some of the material is covered in other sources, for example John Palmer's book, but not all of it.
In part two, each chapter covers a beer style, and there are 14 chapters in total. (Some chapters sneak a couple of related styles in.) The styles covered are mostly British and German. Within each chapter there is a historical overview of the style, some discussion of where the style is now, and lots of statistics. The stats are things like how much of a given grain or hop is used on average in commercial examples of a style, and in beers which have made it to the second round in NHC beer competitions.
Part two is useful if you want to brew closely to style or for competitions, but I don't often use it. I'll try to explain why with an example. On the page 165 there is a table of the incidence and proportion of specialty Malts used in NHC second-round pale ales. In the table we see (among other things) that almost all of them use crystal malt, at up to about 20% of the grain bill but at an average of 8%. A few used Munich malt, but most didn't. Well, that's great to know, but what are we going to do with that information? Probably we'll use around 8% crystal in our pale ales, and leave Munich malt out. This is my problem, despite the book's title there is not really a lot here about designing recipes, it really just guides you towards the style average. I'm sure "average pale ale" is perfectly nice and will do very well in competition, but it's just not what I usually want to brew!
In summary, if you want a book which will help you brew some major styles closely, then this is the book for you, but when you want to go a little off-piste there isn't much here to help you. That said, there is an impressive amount of information in there, and even though I only consult it once in a while I'm glad it's there on my shelf.