What could be an important addition to the body of aviation literature is in fact a disappointment. One expects that "World Encyclopedia of Aero Engines" by renowned aviation author Bill Gunston would have a fair degree of detail on most (if not all) aero engines produced down to the level of different engine models, or a history of those who designed and tested these engines. Instead this book is really just a listing of aero engine manufacturers, arranged alphabetically, and mentions in passing the engines produced by each. Detail is non-existent in many engines mentioned. In the case of piston engines, for example, one is lucky if the author mentions technical specifications such as horsepower, rpm, bore, stroke, capacity, and number of cylinders of the base model. In many cases even this information is partially or completely absent. With a few exceptions, one can completely forget about finding any detail on the different models of a particular engine produced. For example if one wants to know what made the Rolls Royce Merlin Mark III different from the Mk I or Mk II one has to look elsewhere.
However one should give Gunston credit for trying to pull off the impossible. Given the number and types of aircraft engines produced since the beginning of powered flight, producing a true "encyclopedia" would require the team efforts of several authors instead of just one (even one as well respected as Mr. Gunston), and would probably have to be produced in two volumes--one for piston engines and another one for jets and rockets, for example--to give true justice to the subject matter. Instead by attempting to cram everything in to a single slim, 260-page volume quite a bit gets left out. (Indeed of these 260 pages, no less 31 pages are completely blank!) Finally, no bibliography or suggested reference sources are listed, leaving one wonder where Gunston obtained all of his information.
To its credit the book does cover most of the aircraft engine manufacturers worthy of mention, offers a good general overview for those delving into the topic for the first time, and has a useful glossary at the end. Thankfully Mr. Gunston also had the good sense to leave out individual engine "applications," which is a trap that some aero engine authors fall into (since it takes up quite a bit of space with information easily found in existing aircraft books). Also, the price is not bad.