The good: If you want to make cakes just like they have at Dalloyau and Fauchon, buy this book. Divided into: fruit cakes, chocolate cakes, tarts, and petit fours. It tells you EVERYTHING there is to know. The pictures are stunningly beautiful, more so than ANY dessert book I have ever gotten, and I have about 12 or so. The desserts are very original - Pierre uses stuff like saffron and violet, and rose, and all sorts of flowers in his mousses for example. Cool combinations: Chocolate mousse/lemon cream chocolate cakes, genoise/raspberry/orange mousse cakes for example. I am not kidding: if you have this book you will know every single decorating technique, every single way of putting together stuff just as they do in the french bakeries. It lists just about every kind of mousse, every cake you could want, which ways to decorate them, and most importantly how to put it together. This is my favorite dessert book.
The bad: You have to know what you are doing already. The explanations are sparse. For instance, the explanations for pastry cream goes like (this is not real but an example) boil milk + vanilla. Add in whisked yolks/cornstarch. Put back on stove at 120C for a few minutes. Cool to 140 F, then put in butter. So the explanations are very sparse. All recipes are made for 2-4 cakes so you have to scale down. Everything is metric, everything is by weights (so you have to know 1 yolk = 20 g, 1 white = 30 g for instance). Gelatin is used in sheets in the book, so don't forget to put in about 1 T water for every 1/2 t of powder you use (if you're american and use gelatin powder) It helps to have "desserts by pierre herme" by Pierre and Dorie greenspan to "convert" back and forth units, since some cakes are in both books. Sometimes you may want to substitute: ie regular genoise for Pierre's genoise, regular puff pastry for Pierre's inverted puff pastry. In these cases it helps to know what you are doing first.
Overall: The best book period, in my opinion. Definitely worth the extra cost - it is worth 3 regular books. You have to know what you are doing first though, not for beginners. Other recommended books in the same French cake style: "desserts by pierre herme" by Herme and greenspan, and "art of the cake" by bugat and somebody else I forget. Both are great books (and a lot easier), though not as great as this one.