I've had this book just a few days, and I'm already delighted with my purchase. This weekend, my wife and I made two cocktails (The Belgian 75, with gin, lemon juice, sugar, and Duvel; and the Grapefruit Moon, with bourbon, grapefruit juice, maple syrup, and the stout of your choice), and both were out of sight (though I didn't adequately prepare before the night started...remember, people, FILL THEM TRAYS EARLY AND OFTEN. Cocktails need lots of ice). The Belgin 75 was a light, crisp drink that packed a jolly punch, and the Grapefruit Moon had a nice play of subtle flavors, the maple taking the edge off the tart grapefruit and bringing out interesting notes in the stout. There are 48 other recipes as well, many of which sound delicious, including plenty of warm drinks for the cool months ahead. The book is divided into sections by types of beer used, whether it is pale ales or deep lagers, and entire section dedicated to the land with the best beers of all, Belgium. It's probably not a bad idea to make an inventory of your liquor cabinet, as quite a few of these will require multiple ingredients, not all of them common (I need to invest in some Grand Marnier!). There are also several large-scale punches and drinks for four or more, so you don't have to spend the whole night custom-shaking one drink after another if you don't want to.
There's a small intro in the front, explaining briefly some elements of beer making and classifying, and, most interesting to my wife and I, a bit of background on the origins of beer cocktails and the flavoring of beers. If you think this book is some new haute-cuisine bit of flibbery, the Stelzers' history of grogs, drams, and flips in the chilled English countryside will put you on the right path. Beer cocktails aren't a fad, they're a continuation of a very long tradition. Don't worry, purists.
In short: Try it! You'll like it!