A solid, general overview of the science and technology of the steam locomotive, in the format of the Oxford Popular Science series, thus aimed at readers who are scientifically literate (which seems to mean at least high-school physics and a bit of basic engineering knowledge) but don't necessarily have any previous knowledge of this particular subject. Unlike many authors of books on steam railways, they don't take it for granted that the reader is at least as old as the author: they take care to explain things in terms that make sense to someone from the 21st century who has never lit a coal fire or haunted a loco depot. (But they do take it for granted that you have at least a general picture of British railway history and an idea who people like Churchward, Gresley and Bulleid were.)

In line with the authors' backgrounds, the emphasis is on British practice towards the end of the steam age, but there is also plenty of discussion of earlier solutions of the same problems, or different ways of doing things that have evolved elsewhere in the world, with at least a brief explanation of their respective advantages and disadvantages. These explanations often have the ring of real practical experience of what it's like to have to fix these things when they go wrong. The illustrations are well-chosen too, simple line-drawings and detail photographs (mostly taken in the NRM or at big national museums overseas) that clearly show an example of the technology being explained. There are none of those overcomplicated exploded diagrams that should be confined to technical manuals.

Typically, in books on the steam engine (and I've read quite a lot of these, from "engineering for boys" to technical manuals for railway staff) the areas where big difficulties arise in explanation are thermodynamics, injectors, and brakes. Thermodynamics is difficult science, but necessary for understanding efficiency and performance, railway brake systems are generally so complicated in their implementation that it's hard to keep sight of the relatively simple principles behind them, and injectors have a little bit of both, as well as being the one part of a steam locomotive that's completely counterintuitive.

Semmens and Goldfinch do pretty well on thermodynamics and injectors - in both cases they keep the discussion at a high level, don't go into detailed equations and charts and avoid showing us too much of the nitty-gritty of technical implementation. The chapter on brakes, however, isn't particularly clear, and it looks like a bit of an afterthought (arguably it's not needed, as most of it isn't specific to steam traction anyway), squeezed into a rather odd place between a chapter on maintenance and overhaul of locomotives and one on the design and construction of new locomotives. Incidentally, I found those two among the most interesting parts of the book: they are written from the point of view of someone (obviously Alan Goldfinch) who has actually had the job of managing large facilities that are responsible for keeping steam locomotives in working order.

Like many recent books, it shows signs of rushed production, with chapters obviously written as standalone pieces and then squashed together into a book with minimal trimming of overlaps, and a few examples of clumsy pagination around illustrations. The index is a little bit limited too. But none of these issues really has an impact on the usefulness of the book, they just make it a bit less elegant to read.

Omissions: well, obviously, you can't cover everything in 350 pages. It was a bit disappointing that rack-railway locomotives were covered only in a few picture captions, as most of the few newly-built steam locomotives of recent years have been for mountain railways. And it might have been interesting to have a concluding chapter that sums up the technical and economic case for (against!) steam compared to other types of traction - I'm sure that the authors would have found a few myths to demolish there.

This is a book that does what it sets out to, quite pleasantly for the reader. Lots of "why?" and rather less "how?", a good book to satisfy the curiosity of armchair engineers or to read as an introduction if you're looking to go and work on steam locomotives on a museum line somewhere. ( )

Unless you already know how a steam locomotive works, some parts of this book are difficult. However, it is the most accessible technical intro to steam locos that I've found. It could use more and better illustrations. An edition with illustrations by DK would be what I need! ( )