The utility of this book lies in its detailed description of the McMahon line, India's boundary in the northeast. Rich with historical, political, and social information about this geography, it deepens one's understanding of this area significantly. It is also useful for its description of developments inside Tibet right from the early twentieth century and before. It also details the proceedings of the Simla Conference of 1913-14, shedding light on the minutest of considerations of all parties involved.
The anecdotes from the author's own experience with China are interesting as well.
My only major grouse with the book is that it takes the line, more or less, that the India-China boundary has been defined over centuries by tradition, custom, usage. This is a paradoxical statement. A boundary is, by literal definition, shared between two states. Thus, when defining a particular boundary, it must be done by both sides jointly. This has never happened between the Republic of India and the People's Republic of China.
Moreover, whose tradition, whose custom, whose usage? While these are historical facts, there is an element of subjectivity to them. Each side can interpret this statement as per their own whims and fancies, as they have. When they say there is a traditional and customary boundary, they're actually referring to their understanding of the traditional and customary boundary. But this is by no means a shared and joint understanding - which is what it needs to be.
The book is also striking in that it is published in 2019 - post Doklam, pre Galwan. Thus, the recalibration brought on by Galwan is simply not present. It is thus interesting to note the positive mood that was present in the year before Galwan, despite perhaps, warning signs.