Recently picked this book up, as a collector of British (almost exclusively Scottish) badges (as well as Scottish buttons and other Scottish militaria). There are LOTS of books out there on this collecting area, from very small with only a few examples, to large multi-volume works with most every known example. But this is the only one I'm aware of exclusively for World War II units/badges.
Have to admit I enjoyed this book very much. Read the entire book in one weekend. Full color examples of a badge from each British unit involved (does not contain Canada nor others of the British Commonwealth). Does not contain variations, but does contain a brief, though very interesting passage, that explains about the unit's history pertaining to the design of the badge itself. Also lots of period pictures of soldiers wearing examples of some of the badges discussed.
Not a book necessarily for advanced collectors, but an interesting volume about this collecting area with the history behind each badge design.
Enjoyed it so much I ordered the book on the First World War by the same authors.