So, I finally finished reading this! It took a few evenings... Note that I received a review copy of this book.
I should start by saying, I've enjoyed reading a number of books on jet engine development, but I've never read a book on piston engines before. While WW2 aircraft were my first obsession as a kid, I moved onto jets at a relatively young age, and am only now beginning to re-discover this era.
The Secret Horsepower Race is a very readable account of piston engine development on the Western Front in World War II. It's very well written, and proceeds broadly in chronological and narrative form through the pre-war period and the years of World War II identifying key people, events and technologies that influenced the technological development of piston engines in the various nations. It is impeccably researched and referenced, and includes detailed quotes, drawings and charts from source documents to back up Callum's narrative, while most of the major figures in the book are given a small biographical sketch for context.
The book consists of 480 pages, split into 10 main chapters in chronological order. There are copious drawings, photos and charts included, and endnotes give detailed references. There's a list of the archives consulted, and reading through the endnotes shows the immense breadth of research Calum put into the book. This book will be a standard reference for aviation writers engaging with World War II subjects in future, I am sure.
The coverage of engine types is most detailed on German and British engine designs. As Calum notes, some other nations (e.g. Italy) have less archival material available, and he also notes he intentionally covered American developments in less detail as there are already excellent published accounts of their major engine programs available. I also suspect the inclusion of more detailed US engine development history would have increased the page count beyond even the most tolerant publishers' limits.
The cover design is excellent, very dynamic and attractive, it makes you want to pick the book up from the shelves. The page layout is generally attractive, and the text well edited and proofread. Kudos to the Tempest Books team.
The text is laid out with two typefaces used to clearly differentiate between Calum's words and quotes from original documents. For me, as noted by a small number of other readers, the "distressed typewriter" typeface used for the quotes is a little harder to read than is ideal for a book of this length. It didn't affect my enjoyment of the book, and I get the design intention, but given the quantity and length of the quotations included in the book, I think the balance between design for "authentic period feel" and readability was a little off. Your mileage may vary.
In addition, I think that better use could have been made of the captions. Chris Gibson gave me some advice for my book on captions - that they should contain something interesting about the picture or drawing that you won't find from the main text. In many cases, the captions in this book simply tell you what the photo, drawing or chart presented is, but not why it should be interesting to a lay reader. Sometimes you can infer from the nearby text, but not always. So rather than simply say "Fuel evaporation curves from a DB 601 Engine", include a few words on what this chart illustrates for the non-engineer reader. This is especially important for those charts which are reproduced in German - as I often couldn't understand what the labels on the axes were, let alone what conclusion I could draw from the chart.
These are however very minor quibbles on an authoritative and deeply interesting book. 4 and a half stars out of five
I look forward to Calum's next book with great anticipation, and also to future publications from Tempest Books.