While some of the titles could be dusty — The Civil Service in Britain, The Genesis of Modern Management — there were crowd-pleasers too. Putting sex in the title was a good gambit: The Physiology of Sex by Kenneth Walker was published in 1940; The Psychology of Sex by Oswald Schwarz in 1949; Sex and the Social Order by Georgene H. Seward in 1954; and Sex and Society by Kenneth Walker and Peter Fletcher in 1955.

Books about art and artists with black and white and later colour plates sold well. They were slim and light enough to take to galleries. Kenneth Clark, whose life and achievements are celebrated in an exhibition at Tate Britain (until 10 August), gave his name to several titles: The Nude; Landscape into Art; The Gothic Revival and a superb monograph on Leonardo da Vinci. His description of the artist's self-portrait is typical of the book's easy, lyrical style: "This great furrowed mountain of a face with its noble brow, commanding cavernous eyes, and undulating foothills of a beard."

The "look" of the books was always essential to the Penguin and Pelican brand. In the early days, the covers all adhered to a simple orange or blue grid with text in Gill Sans font. Over time, they grew bolder. Black and white illustrations were introduced to Pelican covers in the late Forties, trippy, psychedelic, abstract covers in the Sixties; photographic and witty line-drawn covers by the cartoonist Mel Calman in the Seventies.

There seems to have been no great falling of the axe, just a gradual petering out of the series through the Eighties; the last Pelican was published in 1989. At the time, a spokesman for the firm admitted that the books had become "a bit worthy, a bit hard-going".

The success of the Open University may have taken some of the Pelican market and the boom in the number of students going to university meant that there was less call for people to educate themselves at home. Other amusements and distractions — television, the hi-fi, videos, eating out — may also have done away with the evening at home with an improving book.

Yet now the Pelican flies again. Archivist Steve Hare, who is researching a PhD on Penguin design and has collected more than 15,000 Penguin and Pelican books, says admiringly that this is a "serious and very old-fashioned thing to do".

The new books are not slavish copies of the originals: the blue is lighter, the Pelican logo bolder, the format slightly larger (too large for a back pocket). The designers have perhaps missed a trick with their spare, uniform design. What makes the older Pelicans so appealing to second-hand book shoppers are their distinctive covers. It's easy to be seduced into buying a Pelican with an unpromising title because the cover is so covetable. That's certainly how I ended up with J.H. Plumb's Crisis in the Humanities.

Paul Lickiss, a chemist at Imperial College London and a collector who has more than 1,700 Pelicans, says it is "a pity" to have kept the colour but not the bold, imaginative designs. He singles out The Geography of African Affairs by Paul Fordham, published in 1965  as a witty, inventive example: the letters of "Africa" have been ingeniously stretched to form the shape of the continent.

First time around, it took Pelican a dozen years to abandon purely typographic covers for illustration. No doubt the new Pelicans will find their feet — or should that be take wing?

While writing this article, I found myself, quite serendipitously, on a train opposite a man reading Ha-Joon Chang's new Pelican guide to economics. He was a trainee surgeon, on his way back to London from a medical conference. He was the perfect Pelican reader: educated, inquiring, knowledgeable in one field, curious about others.

When asked what he made of Chang's new blue Pelican, he said carefully that it was "educational . . . heavy-going". But in that crowded train carriage, on a hot June afternoon, he barely looked up from its pages until the train pulled into Paddington. Allen Lane, who built an empire on books that could be read on the train, would have been tickled, if not pink, then certainly blue and orange.