Cressida Connolly: Comfortable, optimistic, safe ÿ oh, for the lost Britain of the Ladybird book

Ladybird books, once grubbied by tiny hands, are now falling into the grasp of collectors. They are mostly thirty- or fortysomethings who, having become parents, are filled with a yearning for the things of their childhood, the days of Shopping With Mother, and What To Look For In Spring, as well as all those Peter and Jane books that helped them learn to read. Collecting them satisfies a half-realised longing for the safe, suburban, Start-Rite world depicted in many of the books.

Ladybirds are also pocket social history. In them you can chart how middle-class Britain changed in the second half of the 20th century. They're fodder, too, for students of gender: from girls in frocks helping Mummy at home to girls in dungarees on Chopper bikes.

There is little of the picaresque in these works, no extraordinary feats, wizards or magic. The strength of Ladybirds is not to depict an imaginary world, but to reinforce a child's sense of the known. This makes their illustrations different from those of many other favourites: think of Arthur Rackham's fairies, E H Shepard of Winnie-the-Pooh, or modern favourites such as Raymond Briggs. These illustrators are idiosyncratic; the whole point of Ladybirds is that they are not.

It takes a practised eye to tell one Ladybird illustrator from another. Chief artist Harry Wingfield and Martin Aitchison contributed most of the pictures for the Key Words Reading Scheme series, which are the best-selling (85 million, to date) where Peter and Jane are featured. Wingfield is masterly at detail: the angle of a child's head, the tips of fingers poking through a home-made glove puppet, the light catching a milk bottle. Aitchison – a former fine artist who exhibited at the Royal Academy – is strong on composition, movement and atmosphere. Their pictures are classic Ladybird.

The appetite for Ladybirds is being fed regularly. Radio Four recently broadcast a programme about Ladybird. Earlier this year the New Art Gallery in Walsall had an extremely successful exhibition of Harry Wingfield's work. Wingfield died before the show closed and his studio has now been bought, wholesale, by Walsall. There's to be a Ladybird conference. There are websites. There are swapfests. And I'm co-curating an exhibition of some 60 original illustrations by three of the main Ladybird artists opened in Cheltenham last week, and will tour Britain over the next year.

The exhibition will reveal another side of the Ladybird coin. As well as Peter and Jane, the firm produced books about topics such as nature and animals, trains and cars and how things worked. A series entitled People at Work described various occupations such as fireman, postman and railway porter. Others in the series – entirely illustrated by John Berry, who had been an official war artist – depict a world of work that barely exists any more. Conceived in a spirit of post-war optimism and expansion, these titles form an almost complete record of British industry at the time. There is coal-mining, pottery-making, shipbuilding. This is a world in which people made things with their bare hands: men in brown coats designed new cars by shaping lumps of clay. Vast swaths of countryside were paved, without apology, into new trunk routes. There is no eco-awareness – or computers or asylum-seekers – here; it is a world in which the most taxing thing a customs official had to do was shine a torch into a woman's handbag. There is a dash of heroism about these jobs. They show the things that children used to say they'd like to be when they grew up: a nurse, an engine driver. Today's equivalents – the call-centre operative, the internet salesman – seem lustreless by comparison.

These books and most of their ilk are out of print today. The firm gets quite testy when pressed about its backlist, insisting that it's not interested in becoming a nostalgia publisher. With radio programmes, exhibitions and collectors clamouring, what I wonder is: why on earth not?

"The Art of Ladybird Books", 15 June - 25 August, Cheltenham Art Gallery, Clarence Street, Cheltenham GL50 3JT.