It's a weird mark of the success of this week's book - and also a shame - that if you search for Thomas the Tank Engine on the internet, you find hundreds of spin-offs and related pieces of merchandise, while the actual book itself is oddly hard to track down.
Why do people love Thomas the Tank Engine? Surely it's because, first published in 1946, it keeps alive the golden age of the railways, when trains ran on steam and actually chuffed properly, and when stations had controllers in top hats who smoked cigars.
Thomas wasn't intended to be the dominant character among the cast of engines, trucks and, later, diesels that shunt around the fictional island of Sodor. The very first book in the Railway Series by the Rev. W. Awdry was called The Three Railway Engines. Published just at the end of the second world war, it introduces kindly Edward, proud strong Gordon, and Henry, who doesn't want to leave his tunnel. We also meet the Fat Director of the station - who later became better known as the Fat Controller.
Thomas only makes his debut in the second book, in which he cheeks Gordon and gets pushed around (literally) by 'silly and noisy' trucks. The eager, self-important little engine who longs to see the world was an immediate hit, and although Awdry went on to write a total of 26 books about all the trains, Thomas became the face of the series and got his own TV cartoon series, Thomas & Friends, in the 1980s.
Today, Thomas is an icon, with Thomas-themed merchandise in every toyshop and kids' clothes store.
Rereading Thomas reminds you why little people love playing with train sets. Children recognise themselves in the strong personalities of different engines, which in these books clearly resemble toy trains, and have expressive faces.
These fictional trains puff, chuckle, whistle, bump, wheesh and peep, blow smoke at one another and pull grumbling coaches. Just like people, they have emotions - sometimes they don't want to get started in the morning; sometimes they're in a terrible hurry; sometimes they show off.
So who was the man who dreamed up Thomas the Tank Engine? Well, he was a country curate, but also, as with so many children's authors, he was a parent trying to entertain his child. In 1943, Christopher, then aged three, had measles, and his father Wilbert, a keen railway enthusiast, made up stories about engines. These were inspired by his own childhood, growing up near Box station in Wiltshire, where he used to listen to the trains as he lay in bed at night.
He later wrote: "There was no doubt in my mind that steam engines all had definite personalities. I would hear them snorting up the grade and little imagination was needed to hear in the puffings and pantings of the two engines the conversation they were having with one another: 'I can't do it! I can't do it! I can't do it!' 'Yes, you can! Yes, you can! Yes, you can!'"
His wife encouraged him to write down his railway stories and send them to a distant cousin, a literary agent. The series would last until 1972, with the most famous illustrations done by C. Reginald Dalby. When he grew up, Christopher Awdry wrote more in the series, but sadly, by the late 1990s, most were out of print. Happily, in recent years, they have been brought back in their original, unusual landscape format, which is so much a part of the pleasure of these books.
Wilbert Vere Awdry was born in 1911, and died in 1997. He once wrote of his success: "In my study at home I have a thick heavy file which I prize highly. It is full of letters. They are from children, mothers, fathers, grandfathers, grandmothers, aunts and uncles who have written to me over the years to say how much they and their children enjoy the books. I prize these highly of course; but there are some I value even more. They are letters from fathers or grandfathers who are or have been professional railwaymen, saying that they too like the books...That is praise indeed!"
Thomas the Tank Engine is published by Egmont (£4.99).
If your child is a serious fan, look out for the classic boxed set of Railway Series books published by Egmont (£111.90) and also Thomas the Tank Engine: The Complete Collection, a one-book edition of the Rev. Awdry's books complete with a map of Sobor (Egmont, £29.99).
You can read more book reviews by clicking on this banner