Not gonna lie, I didn't read the whole book. I flipped through the prologue, skipped part one entirely, and skimmed the epilogue, mostly because I was only interested in part two.
Tallis, as he explains in the preface, "take[s] issue with…. twentieth-century Counter-Enlightenment thought, which is characterized above all by skepticism, or even hostility, towards the idea of a human being as a conscious, rational agent and of human society as susceptible to a progressive improvement as a result of the efforts of conscious, rational agents” (xiv). As such, part two is his critique of what he calls "the marginalization of consciousness." He sees many current intellectual trends—namely, Marxism, psychoanalysis, (post)structuralism, and cognitive psychology and behaviorism—as being dangerous in their repudiation of Enlightenment ideals of progress, reason, freedom, equality, humanism, democracy, science, etc.
I won't go into his specific criticisms of each movement, as that would take too long; instead, I'll summarize the main similarities: (1) the discrediting and minimizing of consciousness is itself a conscious process, and could not occur if we were not rational, ironically (2) anti-individualism is usually espoused by influential individuals, doubly ironically (3) a one-sided emphasis on systems and structures leaves people powerless to change them. In chapter 10, he reduces his entire problem with the critics of consciousness into one sentence: Ideological reductionism is harmful and self-defeating. The apotheosis of Language, History, Society, the Unconscious, etc. inevitably oversimplifies reality and strips us of agency, overlooking the specificity of human experience.
One could reasonably argue that Tallis is attacking straw men or simplifications of complex theories. Though, of course, Tallis himself acknowledges this possibility, and freely admits that, being unable to read everyone's œuvre, he can only address the general ideas and not all their intricacies. To use two examples, one could show, contrary to Tallis, that Marx did not, in fact, hypostatize history (at least in his early, humanist phase), but was extremely critical of this very move, emphasizing the agency of individuals; and also that, toward the end of his career, Foucault changed his focus from how power is exercised over people by institutions to how power exists in the hands of individuals themselves and their capacity to shape themselves as subjects, etc. I'm sure scholars of Derrida, et al., could summon other such clarifications. However, this misses the point. Again, Tallis clarifies that he is not really attacking Marx, Durkheim, Saussure, et. al THEMSELVES, but rather Marx-ism, Freudian-ism, structural sociology, Deconstruction, etc—that is, the ideologies that have been fashioned in their name, and which have often perverted the sources.
I quite enjoyed part two, but I cannot speak about the rest (i.e., the majority) of the book, so take from this what you will lol.