These books are companion volumes to the same author’s Macrolichens of the Pacific Northwest (with Linda Geiser; McCune & Geiser Reference McCune and Geiser2009) but whereas that book was a handy, paperback field guide as well as a laboratory manual, this publication, in hardback and weighing a combined 3·0 kg, comes firmly in the latter category.

The arrangement of content within the two volumes is as explained in their titles: Volume 1 is mainly taken up by keys to genera but also includes an introduction, a glossary, a list of references and an index to both volumes, whereas Volume 2, apart from two pages of general references (references to individual genera are given at the end of each generic account) and the same index that was included in Volume 1, is entirely taken up with the keys to species.

The introduction in Volume 1 includes sections on lichen taxonomy and systematics, the geographical coverage of the books, and lichen chemistry (including an extensive description of thin-layer chromatography (TLC)). The main section of Volume 1 is the keys to genera, although many species are also keyed out. These are indented but also numbered, which makes them easy to use. The keys are laid out on the left-hand page with the right-hand page completely given over to a minimum of eight, high-quality colour photographs of everything from images of macro-scale thalli or apothecia to micro-scale images of apothecial and thallus sections or ascospores. The photographs are quite small (c. 5 × 7.5 cm) but they are also available online at the digital photograph library of Pacific Northwest microlichens, hosted by Oregon Digital, a service of the Oregon State University Library (https://oregondigital.org/sets/lichens-pnw), where they can be viewed at a larger scale. This digital collection currently has 5216 photographs, mostly of specimens collected from the Pacific Northwest and the majority taken through a dissecting or compound microscope. The Library includes many additional photographs not included in the books; for example, there are three photographs of Agonimia tristicula in the books but 11 in the online depository. The 19 page glossary that completes Volume 1 is also extensively illustrated with colour photographs.

The keys to species in Volume 2 are arranged alphabetically by genus and are of the same indented numbered format as the generic keys. However, they occupy both right- and left-hand pages and are illustrated by 479 greyscale photographs or line drawings, which although not as comprehensive as for the generic keys are still considerably more than those in many similar books. Also included are several tables giving the chemical composition of species within a range of genera (e.g. lobate Lecanora, Lepraria, Porpidia, Psora, etc.).

A total of 1721 species are covered (compared to 586 in the “Macrolichens” book); all 1424 species reported from the Pacific Northwest region have main entries, whereas an additional 297 species that have been reported from neighbouring regions with possible occurrences in the Pacific Northwest have secondary treatments. This threefold increase in the number of species covered compared to the Macrolichens book has necessitated a change in format, most obviously in the separation of the generic keys into a separate volume, but also a change from the traditional “flora” style of the previous book where the treatment of each genus begins with a generic description followed by a key to the species, then each species described and illustrated individually on a single page. Here the generic description is retained and enlarged to include additional information, including a “Tips” section that gives informal notes on the genus, but the species descriptions are included within the keys. This works well when the keys are being used to identify an unknown collection but in large genera it can be difficult to find a description if you already have an idea of which species you have and just want to check a few descriptions.

Many recent splits are accepted and these are keyed out both as separate genera as well as within the larger traditional genus; for example, Hydropunctaria and Wahlenbergiella are treated as separate genera but are also keyed out in Verrucaria. However, the recent splits in Buellia and those in the crustose Teloschistaceae are not taken up. This is understandable but it would have been useful to include the segregate genus names as synonyms. The recent splits in Aspicilia are also rejected and new combinations in that genus are made for Circinaria arida and C. elmorei. The artificial separation of Arthothelium (muriform spores) from Arthonia (septate spores) is also rejected and Arthothelium dictyosporum and A. norvegicum are transferred to Arthonia, although whether this is advisable before a full revision of the Arthoniaceae has been carried out is debatable. Interestingly, this is not done for Amandinea, where A. lignicola is retained but other species transferred to this genus (including Amandinea coniops, the type species of the genus) are retained in Buellia or Rinodina. In addition, Tephromela septentrionalis is transferred to Calvitimela, and three species (Lecanora pannonica, Lecidea sarcogynoides and Scoliciosporum gallurae) are reported for the first time from North America.

The change in format necessitated by the three-fold increase in species covered since the Macrolichens book means that these volumes resemble more annotated, illustrated determination keys rather than a traditional Flora. The books are intended largely for use by serious amateurs or professional lichenologists; characters used in the keys can frequently only be observed using a compound microscope and TLC is required for some genera. They are obviously indispensable to any lichenologist with an interest in the lichens of the Pacific Northwest (Oregon and Washington, inland to western Montana and north-western Wyoming, and dipping into north-western California) as well as adjacent areas of British Columbia. However, the phenomenal amount of information assembled and presented by the author makes these books of value to anyone working with crustose lichens and especially for any lichenologist working in, or with an interest in, western or northern North America. They will also be useful to lichenologists throughout the Northern Hemisphere and the descriptions and photographs will be of value to lichenologists worldwide.

In short, these books are highly recommended. The high shipping costs may deter potential purchasers outside the US but this is the cheapest shipping available from the US Postal Service and group orders for multiple copies at a reduced rate are available via the publisher’s website.