As other reviewers have pointed out, it's a good idea for the reader to have several years of all-grain brewing experience. That, and an existing appreciation of abbey-style beers; words alone cannot adequately portray the unique flavors of Belgian fermentations.
Homebrewers often set out to create trappist-inspired beers with the goal of high alcohol content. From reading the book, one will learn that this is a flawed approach; these beers are about allowing the yeast to contribute flavor and attenuation, about embracing the quirky qualities of the yeast, and about retaining balance and "drinkability" in the beer. Higher alcohol content is serendipitous, but almost incidental.
Insightful interviews with trappist brewers, and secular brewers of superb abbey-style ales, introduce the reader to this brewing "philosophy." These discussions, and the technical data of the beers they brew, are of enormous value. (As are the lessons they learned from brewing less-than-spectacular beers.) In fact, the differences in malt bills between the two schools is radical at times. I found it amusing that many of the most revered examples of the styles do not fit neatly into the "guidelines" that are supposed to define them.
All aspects of abbey-style brewing are explored in depth... from water, ingredients, and mash temperatures to pitching rates, influences on yeast behavior, and bottle conditioning. Questions about two of the most controversial topics among homebrewers... yeast origins and sugars... are definitively answered.
Finally, the text is a joy to read! At once both thoughtful and passionate, the book conveys the reader on a journey of exploration and teaching. (As of this writing, my copy is only a few months old, and already frayed and littered with page markers.) It is amazing that such a wealth of useful information can be packed into under 300 pages and still remain so interesting and approachable.
In my fifteen years of homebrewing, I can think of no other publication that is as captivating and enlightening as Brew Like A Monk.