The first edition was just about N.American steamers, mostly West Coast US and Canada. The preface to the 2nd edition says it has been expanded to other areas. I have not read the whole book, but I'd say it is still primarily N. American oriented. Not being an expert on European or British steam practices, I can't comment on whether or not the author's claim to cover other areas is valid. I imagine the boilers and appurtenances sections would be valid anywhere, as are the compound engine diagrams.
The writing is not clear in some places, and I have had to go over sentences several times to see what the author is getting at. Better punctuation would have helped. He was a sailor, not an English major :-). He did start his career on steam, so I trust his writing.
In spite of the occasional turbid nature of the writing, I still feel the book is worth the $ (Amazon sells it also). The diagrams are helpful, and there are lots of photos. It's the first clear explanation of the lever-style paddlewheel engines, as used in the US riverboats, I have read. I'd rate the book at intermediate level - not as detailed as engineering textbooks, but more detailed than beginner steam books..