The fall of the House of Windsor will at the time appear inevitable. But the precise causes, when subsequent historians come to tease them out, will still lack clarity. To what extent did the dynasty auto-destruct, blundering away the natural advantages of its position in a display of vanity, greed, petty squabbling and iffy morals? How did ‘public opinion’ affect events? How significant was the intellectual tradition of radical republicanism? (An easy one, that.) How important was Rupert Murdoch? Andrew Morton? The Sun? Anna Pasternak? What specific weight should be ascribed to colonic irrigation, Susie Orbach and Laurens van der Post in the weakening of the monarchy?

Even when the larger lines of cause and effect seem to have been established, there will remain dozens of questions about the intellectual origins of the revolution. How many people used to read the Sun – and how precisely might the phrase ‘to read the Sun’ be construed? Did readers treat it as a newspaper of record or as a jocund scandal-sheet – or did they do both at the same time, in that state of mental bifurcation common in reality and frustrating to historians? Was this same state operating when half the nation watched Di speak in the tongues of soothsayers and therapists? And how, finally, can those future historians project themselves back into the minds of late-twentieth century Britons who were subjects and not yet citizens; how can they imagine what it was like to be constantly washed over, like floppy sea anemones, by the bilgey tides of royal tittle-tattle?

Robert Darnton confronts such questions, but with much higher stakes: in his case, the historical consequences are enormous, the examined subjects more opaque, the documentation often frustratingly absent. He begins his study of clandestine bestsellers in pre-Revolutionary France with the question posed by Daniel Mornet at the start of this century: what did the French read in the decades leading up to the Revolution? Certainly not what we now think of as ‘eighteenth-century French literature’ – that was a later construct. In the face of the traditional and seductively plausible belief that the great Enlightenment texts, once diffused and absorbed into the social body, ineluctably set off the events of 1789 (and 1794), Mornet produced a sensational statistic. He compiled a list of all the books from pre-Revolutionary libraries sold at auction, and totted up how many copies of that well-known handbook for revolutionaries, Rousseau’s Social Contract, appeared in the catalogues. Result: out of 20,000 books sold, there was only one copy of the Social Contract. So was the Revolution after all not ‘la faute à Rousseau’, or ‘La faute à Voltaire’ either?

Mornet’s finding was in some ways flawed (he ignored collected editions, Rousseau’s subsequent reworking of the Contract in Emile, and also the fact that auction catalogues had to be submitted to the censor), but it energised historians and has been perplexing them ever since. If, as Mornet’s other statistics show, the French spent the pre-Revolutionary years reading the sentimental novels of Mme Riccoboni and the adventure stories of Thémiseul de Saint-Hyacinthe, then shouldn’t we reassess the great intellectual primers in their role as provokers of revolt? Or, to turn the question round, what if the Revolution had different intellectual origins from the ‘high’ ones of the Enlightenment: what if the stuff people actually read, the forgotten pap which circulated without official permission or much critical discussion, was actually more subversive than had been previously imagined?

Robert Darnton has spent twenty-five years on this current project, much of it in the vast archives of the Société typographique de Neuchâtel, a publisher and wholesaler whose list was (as far as we can tell) probably representative of pre-Revolutionary distributors. A quarter-century of research must tempt and bully any normally fallible historian towards some sexy new conclusion. Darnton impressively resists this, and shows a sure-footedness around intellectual potholes. For this is the land of la question mal posée, that smooth invitation to the false answer. Aware of this, Darnton consciously sets his targets low at the beginning: an investigation into the forgotten literature of a period may end up telling us no more than what such literature was like.

Not that this need be dull: and Darnton’s opening chapters on the precise way in which books were authorised (or not), published and distributed is a compelling justification of all his archive work. Most books of significance or interest at that time were circulated clandestinely (though with varying degrees of permission or impermission). The trade’s euphemism was ‘philosophical books’ – which were indeed sometimes works of dangerous thinking, though just as likely to be porn or scandalous accounts of life at court. In this pre-Waterstone’s age, booksellers were often publishers as well, and the whole system of exchange, pricing, marketing and distribution feels a world away. The publishers’ rep trundling glumly round the shires with vanloads of first novels might reflect on the infinitely less secure life of his predecessor: a (presumably illiterate) peddler, raised, say, in the smuggled-silk trade and now diversifying into books, might find himself branded and sent to the galleys if caught on a mountain pass with the wrong type of cargo.

At other times it is the unvarying nature of the business that strike one. The bookseller in Melun who writes complainingly to Neuchâtel that ‘Your catalogue contains nothing but ordinary books’, whereas his customers require ‘the other sort, philosophical books’, is not very far from the porn-seeker pleading for ‘something stronger’. And how about this, from M André of Versailles, as a universal professional credo: ‘I don’t neglect the sale of books that I myself would never read … because the best book for a bookseller is a book that sells.’

The Société typographique de Neuchâtel bestseller list for the period 1769–89 is headed by Mercier’s L’An 2400, the Anecdotes sur Mme la comtesse du Barry and d’Holbach’s Système de la nature; the main classes of clandestinity are political and social philosophy, court memoirs, erotica and anticlericalism (though these last two categories are often inextricable). A second list, that of top authors, is unsurprisingly headed by Voltaire; but in general the big books and hot writers of pre-Revolutionary France have been forgotten. Darnton exhumes, inspects and excerpts three typical works, asking whether perhaps their content was more disturbing to the social order than their current obscurity might suggest. (In the same way, future historians may hunch over Cookson, Archer and Taylor Bradford to see what might have sparked dissatisfaction with the House of Windsor.)

The results are of moderate, though piquant interest rather than of vaster consequence. Mercier’s L’An 2400, a twenty-five-edition runaway bestseller, is a Utopian fantasy of a France without poverty or priests, prostitution or dancing masters, foreign trade or credit, tea, coffee or snuff (which destroys the memory). Inventive but artless, it has its sinister aspects (a Stasi-like network of informers and moral censors, a state reading list greatly reduced by the destruction of all nefarious or tendentious books), though the significant point is that this Utopia came about not by popular uprising worthy of imitation but by the wise and disinterested action of a philosopher-king in renouncing his power. Thérèse philosophe, a book to be read ‘with one hand’, as Rousseau put it, mixes copulation and metaphysic to occasionally witty effect (a priest convinces a skirt-raised seeker of transcendence that the scourge she is receiving is ‘the hardened segment of the original cord that St Francis wore around his habit’). The question of how feminist and socially yeasty such male-directed porn might be leads Darnton into rather solemn mode. Thérèse, a pliant receptacle for most of the novel, ends as a kept woman in a chateau on terms dictated by her lover the count. But might not the fact that Thérèse, rightly fearing childbirth, insists upon a future of mutual masturbation rather than full intercourse mean that she ‘speaks for the right of women to pursue their own pleasures and dispose of their own bodies’? Perhaps. Or is this ending – of partial female empowerment, to use the jargon – as much of a male-stroking fantasy as what precedes it? The question hangs in the air, not least because we don’t know exactly how such literature was read; that’s to say, where the mind was, wherever the hand might have been.

Darnton’s third example, the Anecdotes sur Mme la comtesse du Barry, belongs in the area of the libelle (a word implying the political rather than the private attack) and the chronique scandaleuse. This was contemporary history – which scarcely existed as a genre anyway – reduced to saucy anecdote, affairs of state to ‘private lives’. Those keen to argue the moral decline of the monarchy would find rich evidence here: the traditional role of upper-crust royal mistress usurped by an arriviste whore; Louis XV as doddering manipulee; his court a pack of despotic, self-serving rogues. But did spicy stories such as these, published the year after Louis XV’s death, have a hand in bringing down his successor (was it the Sun Wot Done It?)? How, in any case, might we separate the effect of the deeds themselves from the effect of the literary representation of those deeds? As Darnton admits, ‘We do not even know how it was read.’ His caution is as admirable as his diligence: he is like a plumber tracing a history of drips while refusing to admit the householder’s demand to know that this or that particular drip led to the house-wrecking burst pipe. We may finish his book without grand conclusions, or specific answers, but we also finish it with a sense that Darnton has at least supplied us with la question bien posée.