The book is primarily the history of a name: how did certain people in North Africa come to be called "Berbers", and how did the reference and connotations of this label change over time? Viewed as such, it has a good deal of useful material. He argues that, rather than being derived directly from Latin or Greek "barbari", the label was transferred from East Africa to Northwest Africa as the Arabs moved west; its original associations would be with slavery rather than with barbarism as such. (Traces of the original usage persist: in Nubia, as I first learned on a trip to Aswan, "Berber" is still understood to mean "Nubian"!) In the early medieval period, it was used primarily for rebels and enemies on the fringes; groups with a closer involvement tended to be referred to by more specific terms. Ibn Khaldun's usage is more complex, reflecting Andalusi practice as it emerged in the context of elite competition between Berber and Arab noble families, but shows clear traces of the older tendency to reserve it for "outsiders" to the ruling elite. The modern European usage of the term comes essentially from Ibn Khaldun as filtered through De Slane's essentialism (which turned Berbers into a "race") and subsequent academic and ideological debates, largely in the context of the French colonization of Algeria.
In the penultimate chapter, however, he lays his cards on the table, presenting the term Amazigh as a mere relabelling of the neo-Khaldunian concept of "Berber", constructed with insidious intent and making an already misleading discourse even more ahistorical:
In the early 1950s, a few specialists proposed to replace “Berber” with “Amazigh,” the name some people in northern Morocco had.... “Amazigh” could not fully conceal its colonial birthmark, however. Its rejection of Arab imperialism of centuries past, its search for an authentic indigenous category, and its reliance on the fruits of colonial historiography, epigraphy, and linguistics to do so are all telltale signs. Calling for name change could have led to the realization of the historicity of all names and from there to the historicity of Berberization. It did not... “Amazigh” (indigeneity) was the parting gift of a dying colonialism to the frail nationalisms it had never accepted. Pulling the rug from under “Algeria” and “Morocco,” which as the colons repeated were new and artificial, “Amazigh” dealt a blow to anticolonial nationalism.
The 2-page discussion of “Amazigh” is unacceptably simplistic, especially after multiple chapters of careful examination of the changing semantics of "Berber". The author would have been better off omitting the term entirely than giving it such a caricatural treatment, massively understating the geographic distribution of the term (not just northern Morocco but as far off as northwestern Libya...); his medieval focus cannot entirely excuse the omission, as this term is (less frequently) attested in the medieval period. A proper examination - and, yes, historicization - would have been all the more valuable given that the term was used as an endonym in many regions long before the emergence of the modern trans-national ideology, whereas "Berber" has not been adopted in ordinary Berber speech anywhere, remaining an exonym, and usually an exclusively learned one at that.
Reading as a linguist, I can appreciate the attention given to semantic shifts and to the arbitrariness not only of the sign but of the signified. But as a historical linguist, it feels rather at cross-purposes to the questions of interest to me. Fundamentally, I don't much care which ethnic label people identify or are identified with: for me, "Berber", like "Arabic", is primarily useful as a linguistic category. And its referent has a history starting far earlier than the earliest attestation of "Berber", "Tamazight", or any other label one might choose to apply to it. It is necessary and appropriate to historicize such labels - to be aware that Masinissa or Dihya or Fatma n'Soumer were not acting in the name of some kind of Amazigh nationalism, and may not even have been familiar with "Amazigh" as a name, let alone as an identity. But how this relatively close-knit language family spread, and retreated, remains a historical question, of interest to archeologists and population geneticists as well as linguists, which an exclusive focus on ethnic labels erases.
It should, however, help to provoke reflection on the appropriate choice of label for this language family. "Berber", neutral though it undoubtedly is in English or French, does have a problematic history; the derivation from "barbarian" may be inaccurate, but this book really underscores the extent to which its usage in Arabic has been overwhelmingly negative and "othering" for most of the region's history. "Amazigh" does not have this problem, but is strongly associated with a projection of shared ethnicity into the past which risks distorting our picture of language spread. In an ideal world, one might prefer a purely geographical label ("Northwest African"?), or, better yet, a purely linguistic one (iles-languages, after the usual word for "tongue"?) In practice, however - here as elsewhere - it seems preferable to live with the occasional misunderstandings caused by the use of a well-known "ethnic" term than to confuse the public with a completely novel one.