In his introduction to The Ragged-Trousered Philanthropists, Robert Tressell's novel about a band of downtrodden Edwardian housepainters, Alan Sillitoe describes how he first came across the book as a 19-year-old national serviceman in Malaya. "You ought to read this," the Glaswegian wireless operator who pressed it on him explained. "Among other things it is a book that won the 1945 election for Labour." Sillitoe doesn't comment on this claim, which in retrospect seems more than a little far-fetched - although first published in 1914, The Ragged-Trousered Philanthropists can't have achieved much circulation until its paperback days in the 1960s. But the story seems to me to illustrate an important point: not so much perhaps that books have the power to change things, but that people think they do, that the average sentient human being's belief in the ability of reading to alter human behaviour is quite as unquestioning as, say, his acceptance of the basic laws of physics.

What are the most influential books published in Great Britain in the past 150 years? Even to ask this question is to run into a cul-de-sac of nuance and definition. Moral influence? Intellectual influence? (These are not quite the same thing, as the merest glance at a book by a self-advertised moralist or intellectual rapidly demonstrates). Practical effect? Defining influence in its broadest sense, something like "demonstrable and measurable impact on human behaviour", my own votes would go to Samuel Smiles's proto-Thatcherite "can do" guide, Self Help (1859), the standard infantry training manual used by British soldiers in the second world war, and the bound version of the Beveridge report - which is cheating, perhaps, but one can grow tired of the inevitable votes for Darwin, Mill and so on.

Certainly these are questions in which Martin Seymour-Smith would have taken a fierce and implacable interest. Seymour-Smith, who died last year - apparently after the jacket of this book was printed - was an old-fashioned literary man of a type that is practically extinct (this is not an insult, by the way, but about the highest compliment I can think of paying him). He was one of those rare specimens who managed to survive for upwards of 40 years on the exiguous proceeds of reviewing and writing serious books on serious subjects.

His forte, as well as heavyweight literary biography (see in particular the lives of Hardy and Robert Graves) was taxonomy: The New Guide to Modern World Literature; Who's Who in 20th- Century Literature - and it is not exaggerating to say that the idea of the literary league table became an obsession with him. He once described Hubert Selby Jr's Last Exit to Brooklyn as being among the six best novels written in the 20th century, a breathtakingly audacious judgement that, whatever the undoubted merits of the book, tells you far more about the person who pronounced it than the writings of Hubert Selby Jr.

If Seymour-Smith was a deeply old-fashioned operator, then The 100 Most Influential Books Ever Written is a deeply old- fashioned exercise. Its ancestors are a whole shelf of late-19th-century and early-20th-century literary self-help guides with titles such as A Library for £5 or The Choice of Books, or perhaps Arnold Bennett's Literary Taste (1909), which instructed its readers how to assemble a library of the 350 finest English books for the rather odd sum of £28.0s.1d. It has, too, that same late-Victorian irascibility, the same brazen confidence in first principles, which occasionally fails to conceal the uncertainties of the reasoning processes behind them. One gets the impression of a man who decided to become a literary critic because it accorded with something absolutely fundamental in his nature, and provided that nature with a fail-safe way of expressing itself.

Inevitably, thumbing through this huge compendium and its century of critico-biographical essays, you return again and again to the question of "influence". Although Seymour-Smith includes the great spiritual texts (Old and New Testaments, I Ching, Koran) and doesn't ignore imaginative literature (The Pilgrim's Progress, War and Peace, The Trial, 1984) his preference is for huge intellects whose thoughts are endlessly diffused through and cannibalised by populist media until some necessarily debased version of them comes to rest in the average human mind. The usual suspects are rounded up - Kant, Kierkegaard, Nietzsche - and the case against popular literature is solidly put. Millions of people have read and enjoyed Gone with the Wind and millions of women may have consciously or unconsciously modelled themselves on Scarlett O'Hara, but this doesn't mean that Margaret Mitchell is an "influence": it is the archetype behind her stereotype that is important.

While this argument is satisfactory as far as it goes, it's difficult not to feel that Seymour-Smith cruelly underestimates the effect of imaginative writing on people's lives, and that this is ultimately far more central to the collective consciousness than pinches of Kant infinitely diffused into the mental water supply. The obvious omission here, for example, is Charles Dickens, about whom Seymour-Smith worries in his introduction. Even now, I suspect, a comedian who went on television and imitated Oliver Twist or Scrooge would stand a fair chance of being recognised, and Dickens remains public property (I can remember Neil Kinnock once comparing Margaret Thatcher to Miss Havisham in an election broadcast) in an altogether conspicuous way. This doesn't mean that he directly influences the way in which you and I think, but it does mean that he helped to create a kind of framework of "Englishness" and national "character".

Meanwhile, I don't believe for a moment that a book such as Betty Friedan's The Feminine Mystique - one of Seymour-Smith's more exotic selections - influenced anybody. I am also ashamed to admit that of the 100 items on display here I have a working knowledge of precisely nine. Nevertheless, however fragmented and decentralised the course of human thought, books such as The 100 Most Influential Books Ever Written will continue to appear. If so, you hope that people like the late Martin Seymour-Smith - driven, word-obsessed, apparently unfazed by the perils of his hand-to-mouth existence - will still be around to write them.

D J Taylor's biography of Thackeray will be published in the autumn by Chatto & Windus