If you're in the market for one of Ferraris covered in this book, you'll find Bluemel's work indispensible. If you want a coffee table book, it's not bad for that either, but ultimately the tables and detail photos overwhelm the pretty car pictures.
The newest 328 is already more than 15 years old, and Bluemel's book will give you a benchmark for how a well-kept, original car ought to look. This is more important than you might think, as the Ferrari owners 'circle' really does care about originality and honest preservation -- if you're a buyer, you'll undoubtedly be more educated after reading Bluemel. Production for the 328GTS, easily the most successful regular production car in this period, was only 6000+ cars over 5 years - paltry compared even to niche companies like Porsche. The Ferrari world is a small world, and an expensive one in which to make mistakes, so consider this your essential desktop reference.
While there is some commentary interspersed regarding aesthetics, there is close to zero information on driving and maintenance, and it is certainly not a buyer's guide listing the weak spots of the various models. Also, even car fanatics are unlikely to read this straight through, as it discusses all aspects of the cars section by section. So unless you plan to go to be reading about the tires and wheels on the 348, for example, it is largely a reference. But at that it is quite a good one, and it gets pulled from my shelf frequently.