Guillaume Jacques's grammar offers a comprehensive description of Japhug, one of the Core Gyalrong languages of the Tibeto-Burman (Trans-Himalayan, Sino-Tibetan) language family spoken in Sichuan Province, China. The grammar is based on oral texts and conversations rather than on elicited material, the data being recorded over nine fieldtrips (2002–2018) and supplemented by constant phone contact with the consultants. Taken together, the amount of data, extensive and long-lasting contact with the language community, and reliance on non-elicited materials archived in Pangloss, mean that the grammatical description rests on particularly solid ground and makes credible claims that can be independently verified. Readers benefit from the hyperlinks in the digital edition of the grammar that connect the examples to the Pangloss archive that hosts the recordings of the original narrations. While archiving at least a part of the original data to a publicly available database has become common practice in grammar writing of less-researched languages, Jacques's interactive approach offers a great illustration of how information technology can and should be used to enhance grammatical descriptions in the digital era.

Descriptive grammars show a decades-long trend towards longer and more in-depth descriptions of their target languages. While the trend is partly due to advances in linguistic research, such as the “epistemicity boom” of recent decades that has benefitted descriptions of evidential systems in languages of the world, the trend also reflects changes in the genre of descriptive grammars, “comprehensive grammars” gaining ground as a prominent subgenre. Jacques's detailed grammar fits neatly into this trend in grammatography and in many ways epitomizes it. With a meticulous and systematic treatment of Japhug grammar, the description not only synthesizes the author's previous work on the language that has appeared in various articles and monographs, but also offers many new contributions, which makes A Grammar of Japhug not only the most comprehensive documentation of a Tibeto-Burman minority language, but also one of the most comprehensive monographic grammatical descriptions of any language in existence. This is all the more remarkable an achievement, since prior to the author's first steps in Japhug research approximately two decades ago, very little was known about the language, and more broadly, many breakthroughs of Gyalrongic scholarship were still to take place.

From the viewpoint of users, comprehensive grammatical descriptions present their own challenges distinct from those of shorter grammars. For instance, while typologists looking for source materials concerning specific grammatical phenomena often lament the incompleteness and omissions that characterize shorter grammatical descriptions, a comprehensive grammar of over 1,500 pages offers a challenge for the reader with no specialization in Gyalrongic linguistics in seeing the wood from the trees. Foreseeing this, Jacques's solution of including a well-formulated and highly informative grammatical sketch (ch. 2) at the beginning works very effectively. This sketch is useful to non-specialist readers in illustrating Japhug's genius of language. It can thus be used for gaining a quick overview of the language and identifying points of interest that are discussed in more detail in the chapters that follow. Of particular interest are the remarkable features of Japhug (§2.8) that illustrate aspects of the language that have high typological and comparative value. Following the grammatical sketch, the rest of the grammar is divided into four main topics of focus: phonology (chs 3–4); nominals and noun phrases (chs 5–9); verbs and verbal morphology (chs 11–21); and syntax covering simple clauses and complex clause constructions (chs 22–26). The grammar ends with a discussion of kinship (ch. 27) and three appendices on names, Japhug forms, and subject matter. The structural choice with emphasis on verbal morphology reflects the high complexity of the verbal domain in Japhug, a feature of all Gyalrongic languages.

A Grammar of Japhug establishes and solidifies terminology for Gyalrongic research, an important task in the relatively young field. The description strikes a balance between using common and widely accepted linguistic terminology familiar to most readers, and coining novel terms or borrowing them from other research traditions when this is needed, particularly when discussing the peculiarities of the Japhug verb. The coined and borrowed special terms are well chosen and informatively named. Many cases, such as tropative (originally from Arabic linguistics) are already familiar from Jacques's previous work. Also, replacing the earlier and potentially confusing status constructus and construct state used in Afro-Asiatic linguistics with different and narrower meaning by bound state (§5.4) is a terminological improvement that helps readers.

In all, A Grammar of Japhug is a remarkable achievement that offers immense contributions to Tibeto-Burman linguistics and is of great value for typologists as well. While every language should be described in its own terms with respect to its particularities, Jacques's landmark description of Japhug will be highly valuable in future descriptive work of other Gyalrongic languages, an urgent task in field linguistics of Southwestern China that will undoubtedly substantially benefit from the publication of the grammar. At the same time, A Grammar of Japhug serves as a model and source of inspiration for both experienced and aspiring grammatographers for years to come.