Clive James cannot write a dull sentence or express a mundane thought. The revered Australian critic and author accumulated the 110 biographical essays that make up Cultural Amnesia over a 40-year period. While also busy publishing some 30 other books, all delivered in the same whip-smart, aphoristic prose, the timeline is helpful in rendering this massive project less daunting. Do the math, and the numbers revert to the human sphere: two or three essays per year, manageable for a writer once described by The New Yorker as a "brilliant bunch of guys."

A compendium of the course of humanism during the 20th century, explored through the lives of artists and intellectuals, politicians and scientists, both famous and obscure, admirable and venal, the book further adds to reader anxiety about size (876 pages of small print) by disavowing any unifying scheme. "The finished work," James writes in the introduction, "if it were going to be true to the pattern of my experience, would have no pattern." The essays are ordered alphabetically, with an overture and coda sketching scenes from Viennese café society – his personal ideal of the humanist paradigm – on the eve of the Nazis.

The experience he is referring to is his own impressive lifetime of reading. As the subtitle suggests, Cultural Amnesia has two bookish ambitions, one private and modest, the other public and grand. Modestly, it is the author's accumulated marginalia, his commonplace book of quotations and clippings. Each essay begins with a quote attributed to the subject, and James is careful to source his first reading, noting down and, often, memorizing of the remark as the start of his engagement.

Immodestly, the book aims to embody nothing less than the shape of intellectual and creative life itself in the last century. In particular, it wishes to demonstrate the perilous state of liberal humanism as a collectively agreed-upon cultural ideal. For all his stylistic dazzle, Clive James is a clear, almost plain thinker about the necessity of acknowledging again and again the multiplicity of the world.

No surprise, this secular faith renders him a fierce critic of any and all ideological gods that have failed, or gods presently in the act of failing. Upon the 20th century's various ideologies, be they catastrophic political experiments played out on a global scale or the illiberal liberalism of much academic fashion, he heaps equal, and equally cogent, scorn. Gurus who preached the ascendancy of a scientific view of human society helped contribute to "flattened cities and gassed innocent children." Academics currently "putting the humanities to careerist use" are furthering an "international cargo cult whose witch doctors have nothing in mind beyond their own advancement."

Here too, the non-structure of the compendium is purposeful. "Modern history has given us enough warning against treating simplifications as real," he notes. Declaring an ideology to be a "premature synthesis," he vows to avoid foisting any such meanings upon his reflections. He also grants that Cultural Amnesia will be a "turbulent read."

"If this book were not difficult," he says, "it would not be true." To wit, the book is turbulent and, in spots, mercurial and intemperate. Throughout, it is also luminous and enthralling, each page a bracing encounter with a charged intelligence.

The range of subjects is humbling. Nadezhda Mandelstam, Albert Camus and Federico Fellini are heroes to Clive James. F. Scott Fitzgerald, Mario Vargas Llosa, Charlie Chaplin and Evelyn Waugh are individuals he largely admires. For Edward Said and Jorge Luis Borges, he has more mixed, if still appreciative, feelings. In Jean-Paul Sartre, he sees almost nothing good, rather part of a crowd of European intellectuals compromised by their bad faith in those various failing gods. Mao Zedong and Adolf Hitler are also treated, with predictable results.

On the mercurial end, there are denunciations of jazz icon John Coltrane for "submitting some helpless standard to ritual murder" and Walter Benjamin for granting licence to generations of academic gobbledygook. Dick Cavett is memorialized for bringing urbanity to North American television and a case is made for Tony Curtis as an American original. Readers are encouraged, possibly even expected, to jump up at any moment with disagreements and corrections.

The essays themselves are performances. Incapable of a dull line – "American dominance of the world's big screens worked by consent," he writes in the entry on Curtis – James is likewise incapable of staying long with any one non-mundane thought about any one thing. His advances from subject to subject within the same essay are always graceful but frequently unexpected. Much of the fun – and some of the difficultly he alluded to – lies in figuring out the direction, and intent, of his turns.

In the Camus essay, for instance, a citation from The Rebel about how tyrants "conduct monologues above a million solitudes" births a paragraph detailing James's youthful fascination with "the trench coat and the Gauloises" of French radical chic. Thoughts on the "power to bore" of totalitarian overlords compels a shift to the speeches of Stalin and Mao's Little Red Book. Soon enough, the tedium, and weird allure, of Fidel Castro is probed, followed by a lament for the suffering of North Koreans under the prose yoke of Kim Il Jung.

"Not a paragraph of it was of any interest whatsoever," James notes of Kim's voluminous utterances, all mandatory reading for his luckless subjects, "except as an awe-inspiring demonstration of the great leader's prerogative to bore his people rigid, like the Chinese terracotta army he inspected on his tour of Shaanxi province in 1982. He must have thought he had seen those glazed eyes before."

Asked how anyone could get through Finnegans Wake, James Joyce famously answered that since he had spent 20 years writing the novel, readers could spend 20 years reading it. While there is nothing, mercifully, late Joycean about Cultural Amnesia – indeed, the essays are uniformly pithy and welcoming – the broad point might still be valid.

An argument could have been made for "telling" the tales of the book chronologically, thus allowing these individual lives to be assigned their spots in the historical continuum. By opting for an alphabetical arrangement, James is encouraging readers to dip into and out of both the narrative and the century itself. Forty years of writing in trade for 40 years of reading? Not necessarily. But declining to forget the past is surely an ongoing project. Let this curious and remarkable work be a buttress against amnesia, as well as a paean, its refrain well worth repeating, to a cultural ideal that seems more and more at risk.