ON August 27, 1914 - 100 years ago - the British Library in London received two recently published children's books to be lodged, as the law required, in its massive print collection.

Alongside the thousands of other publications, including first editions of the most famous works ever published in English, these books wouldn't have amounted to much.

The company behind them, Loughborough printers Wills & Hepworth, certainly didn't much of it. The First World War had just begun and, though paper was becoming increasingly scarce, demand for reading material was soaring. Slim volumes intended for small hands and young minds, the books had been hastily commissioned and were poorly written because Wills & Hepworth had seen a gap in the market and were trying to fill it. Quickly.

But like some of the great works they nestled alongside in the British Library archives, these two modest offerings - Tiny Tots' Travels and Hans Anderson's Fairy Tales - do now have a revolutionary tang to them. Why? Because they were the first in a long-running series that would become an integral part of the childhood and education of millions of children. Generations of young readers would grow up reading them and, though hundreds of different titles were published, they would come to be known by one catch-all name, that of the tiny red and black insect whose image adorned their covers - Ladybird.

In its centenary year, it's fair to say Ladybird isn't the force it once was. Books are still published bearing the famous logo and the imprint has embraced the digital age with a website and an app. But despite being absorbed into publishing giant Penguin in 1998, the titles are fighting for space in a marketplace ever more crowded and competitive.

That wasn't always the case, however. For many decades - and for a golden period from the end of the Second World War until the early 1970s - Ladybird Books were on (or within reach of) the bedside tables of virtually all British children. From nursery rhymes and fairy tales to potted biographies of historical figures and guides to everything from flowers to flags, they provided information and learning alongside vivid illustrations. It was a winning combination.

Another part of their appeal was their cheapness. The price stayed commendably constant for about 30 years, first at two shillings and sixpence and then at its decimalised equivalent, 12-and-a-half new pence.

The size suited people's pockets too. From 1940 onwards the books were produced in a manageable four-and-a-half by seven-inch format. They would fit into a blazer or, for those like me who came to them in the 1970s, the side pocket of a pair of Birmingham bags.

Sales went from 36,000 copies a year in 1946 to around 400,000 in 1949, a healthy enough increase. But by 1971 the number of copies sold annually had soared to around 20 million, in large part because the books were no longer just on bedside tables but on school desks as well thanks to the company's seminal Key Words Reading Scheme. This introduced young children to the world of siblings Jane and Peter, and their dog, Pat. Peter and Jane's daily potterings to the sweetie shop, the park, the beach and the fairground were used as a platform on which to teach the ABCs of reading and writing and it's probably these books more than any others which have come to typify what Ladybird stands for.

In The Ladybird Story, a new book published to mark the centenary of the series, authors and Ladybird scholars Lorraine Johnson and Brian Alderson note that the Key Words Reading Scheme was both "ambitious" and "perhaps notorious". It was ambitious because it proposed teaching children to read using a system devised by educationalist William Murray based on the idea that very few words make up most of conversational English.

And notorious? Well, as anyone who remembers Peter and Jane will know, the universe they inhabited was as far from real life as Midsomer Murders is from The Wire. It was very white and solidly middle class. It was also regimented, ordered and, frankly, a little dull. Sure, children could play in the street and walk to the park on their own, but otherwise theirs was a Watch With Mother world where childcare was entirely a distaff concern and it was the suited dad who went out to work in order to bring home the metaphorical bacon. If mum wanted the real stuff, she would order it from the cheery butcher on the high street who would probably have his boy bring it round on his bike when doubtless it would arrive wrapped in greaseproof paper and tied with string. Those were the days.

Launched in 1964, the Key Words series continued until 1967 and ran to 36 books. By one estimate, they were in three-quarters of British primary schools by the end of the decade, and by the mid-1970s it was thought around 34 million had been published.

But by the mid-1970s, the backlash was brewing. New ideas about education were coming to bear on the imprint at the same time as new theories about class and gender equality were re-framing public discourse and political thinking. As Johnson and Alderson note rather archly: "The swinging character of the 1960s generated atmospheric disturbances well beyond the nation's dance floors."

In an influential 1974 essay about children's books in which she looked at Ladybird's Key Words series, teacher Glenys Lobban railed against the Ladybird vision of Britain as "a white middle class world peopled with daddies in suits, and mummies in frilly aprons, who take tea on the lawns in front of their detached houses". This image, she argued, was "irrelevant and harmful for urban working-class and black children. They do not provide them with models like themselves, they implicitly, if not explicitly, denigrate these children's culture and imply that what is real and proper is also white and middle class".

It's about here that I enter the picture. I was then, and still am, white and middle class. But I was a member of the collar-length hair and Tiswas middle class, which meant even I was out-of-step with Peter, the suburban square with the old-fashioned haircut.

But still I reached for the Ladybird books. As I write this, I have a 30-strong pile of them beside me. One or two have been picked up in recent years in secondhand bookshops and bought for reasons of novelty value or nostalgia - titles like The Ladybird Book Of Magic Tricks and How It Works: The Telephone, which has a pistachio-coloured 1960s Trimphone on the cover. But I've had most of the books since I was a kid. They have titles like Some Great Men And Women, A Ladybird Book Of Flags (whatever happened to Ceylon and Rhodesia?) and, always my favourite, The Story Of Football.

Leafing through A Book About Pirates I can still access some of the thrill I felt when reading about Red Legs Greaves, son of a Scot sold into slavery in Barbados by Oliver Cromwell. And I can still feel the delicious sense of dread the front cover instilled in me: it shows a cruel-looking pirate cocking his pistol, his face lit by the orange glow from the burning ship his cutlass-wielding men are about to storm. A rowing boat is pulling away from the stricken ship. Will its occupants be slaughtered? Ransomed? Saved? Or is the boat moving towards the ship, a boarding party armed with dirks for close fighting? Like all the best Ladybird illustrations, it's a frozen moment loaded with possibilities for the childish imagination.

Anyway, back to my pile. What To Look For Inside A Church has barely been opened, I note, nor has its companion, What To Look For Outside A Church. Who gave me those? And why? I don't know. But Julius Caesar And Roman Britain bears all the hallmarks of having been read and re-read again and again. Oh, and here's my infant scrawl inside, my name in biro. How old am I there? Eight? Nine?

From this book I learned a lot about Caesar and a little about Agricola. And about Caractacus - "the bravest and most famous" of the British warriors who opposed the Romans, according to the text by L Du Garde Peach MA, Ph.D, D.Litt. I learned enough to make me want to grow a massive walrus moustache and charge at scarlet-clad legionnaires. I went on to study history at university, by the way. Could L Du Garde Peach's prose be the reason?

I'm not alone in having kept my childhood Ladybirds either, nor am I the only person who has enthusiasm for them. The internet is packed with collectors' sites and I note from one of them that my much-loved 1964 copy of The Story Of Football could fetch around £20 if I cared to sell it. I don't, though I could be persuaded to part with my copy of The Ladybird Book Of Motor Cars. It's listed on another website as being a particularly rare item.

Looking closer, I see mine doesn't quite fit the bill: for it to be a truly rare edition it has to meet certain criteria, known in the lingo as "issue points". Mine doesn't. The price is right - two shillings and sixpence - and so are the illustrator (Ladybird regular David Carey) and the series number (584). But if it ever had a dustwrapper it doesn't now and, crucially, the blue Ladybird logo on the "front endpaper" shows the insect with its wings closed.

But it isn't just the books themselves that are sought out by collectors. Original illustrations, particularly ones by the 1960s trio of Harry Wingfield, John Berry and Martin Aitchison, are highly collectable. Acclaimed British visual artists Gavin Turk and Fiona Banner are both fans and even a decade ago an exhibition of original illustrations by Berry and Aitchison at London's Simon Finch Gallery had prices starting at £1500. Wingfield, meanwhile, was given a major solo retrospective at the New Art Gallery, Walsall's swish, Lottery-funded contemporary art centre in 2002. He was 91 at the time. Late recognition, perhaps, but recognition nonetheless.

My eight-year-old son is about the same age I was when I started scrawling my name in my Ladybird books. His childhood is very different from mine, though: no iPads or Minecraft or Angry Birds in my day. But he does like the Ladybird Book Of Magic Tricks and has even mastered a few of the moves, tricks he trots out from time to time to my great (if feigned) amazement. Times may change, but boyish glee looks the same in any decade. Perhaps, then, the Ladybird's wings will keep it flying for a while yet.

The Ladybird Story: Children's Books For Everyone, is published by British Library books, £25