Although this is the first edition of this publication, it is the second edition of the keys which appeared first in the renowned and excellent Lichens of North America (LNA) published in 2001. The problem with that book is that it only contained, and can only contain, a fraction of the species known from North America, otherwise it would require a truck to cart it around. So this book addresses this problem and almost doubles the number of species included in the keys, from 1086 in LNA to 2028 species. Even so, with 4881 species having been reported from the continent, less than half the species are included. But this does not mean that the keys will only be good for half the lichens encountered because the species are chosen especially for the frequency and likelihood of being collected. For cross-reference, the species illustrated in LNA are printed in bold. This book looks to be very useful indeed, especially as an accompaniment to LNA.

The keys are arranged into 11 groups with a “Key to the Keys”, as is the usual format for lichen keys, and these take the reader to a species or a genus. Then the keys to the genera follow. The generic keys are in alphabetical order and in groups of similar genera so, for example, the Bryoria key includes Bryocaulon, Gowardia, Nodobryoria and Sulcaria. If there is any doubt whether a sought for genus is included on its own or with another, the index will help. This practical approach is a great help today, when DNA sequence evidence places species in genera whose appearance is very similar. There follows 10 pages of literature citations and an index to every species and genus mentioned in the text. The 11 pages of glossary, together with the 37 figures, provide valuable explanatory material to help interpret the keys. Finally, there are 13 colour plates, which help with some of the morphological details and colour lichens portray, and a final photograph of Rinodina spores is an obligatory addition, as anyone who has tried to identify Rinodina species knows. The plates are rather idiosyncratically numbered 9–34, and the final one 925, in the copy I received.

The keys need to be used in conjunction with LNA, which clearly explains in Chapter 13 the techniques used to obtain and observe the features of the characters used in the keys. I would only add one and that is on the identification of confluentic acid, the presence of which is easily determined by applying a 10% solution of sodium hydroxide, which is readily obtained from stores, often as a drain cleaner (rather than potassium hydroxide), to a section under the microscope. If confluentic acid is present, colourless needle-shaped crystals form in clusters. Having tried keying out some specimens from the USA, I found the keys worked well and were easy to use, but I would have liked more information when arriving at a species not in LNA. Clearly space is very limited; the book is large enough as it is, but perhaps some of the information that is duplicated in LNA could be omitted to compensate. For the species not in LNA I checked out 10 species at random and for nine of them, photographic images were posted on the internet although the identity of these and quality of the images is not as reliable as in LNA. The author has steered a careful path between the amateur, who is not likely to use the full range of microscope techniques, and providing enough detail to enable the keys to work satisfactorily.

Any lichenologist visiting, or even thinking of visiting, North America should definitely obtain a copy. It is very well priced and as a working book with spiral wire binding lies conveniently flat on the workbench. Other lichenologists will also find it interesting, as with LNA, and useful, especially when comparing a species as found in North America with the same species found elsewhere in the world.