The Rabbit Hole Book by Richard Coles, Cat Jarman and Charles Spencer: Poirot and the dyeing mystery of his little grey hairs...

The Rabbit Hole Book: 99 Adventures Into the History of Stuff by Richard Coles, Cat Jarman and Charles Spencer (Michael Joseph £22, 352pp) Themes can be overrated. Most books have to be about something – they tackle a subject, make an argument or tell a story.

But what happens if you get three people to do short investigations into random topics for no better reason than because those topics sound interesting? The Rabbit Hole Detectives is what.

The hit podcast is presented by Richard Coles , Cat Jarman and Charles Spencer , and each research something – paperclips, for instance, or jet lag, or pub names – before reporting their findings.

And now they've written a book. It is surely the only book ever to tell you both that Hercule Poirot's hair dye was called Revivit and that the Dobermann dog was originally bred by a German tax collector who needed a pet vicious enough to accompany him on the job.

I'd be amazed if you found all of the 99 chapters interesting – that's the nature of the project. But, equally, I'd be amazed if you found none of them interesting.

My own curiosity gland was tickled by many of the entries, several because they shed light on something I thought I already knew.

The Westminster Abbey funeral effigies, for example. I've read lots about that building over the years, but had never heard of its collection of life-size models of the great and good from centuries past, usually made of wood or wax.

The Duchess of Richmond arrived in 1703, accompanied by her parrot, which died of a broken heart. It is thought to be the oldest stuffed bird in the world.

Equally, the Welsh village Llanfairpwllgwyn-gyllgogerychwyrndrobwllllantysiliogogogoch is well known – but how many of us were aware that it hosted the first ever British meeting of the Women's Institute?

And we've all done crosswords: did you know that the puzzle's inventor called it a 'word-cross'? It was only because a proofreader on the New York World newspaper switched the syllables in 1913 that the modern name came about.

Sometimes, though, the fascination is because the subject is completely new to you. The Panacea Society was a religious organisation started in Bedford in 1919 by Ms Mabel Barltrop.

It sent out to ill people, free of charge, squares of linen over which its members had prayed. If you left your square in a jug of water, went the claim, and drank the contents four times a day, you would get better.

The society also maintained accommodation for Jesus Christ when he appeared at his third coming. Ms Barltrop believed her own late husband had been the second coming.

Numbers feature heavily. We encounter the world's largest pane of glass (50 sq metres, in a Beijing skyscraper), learn how six 2x4 Lego bricks can be combined in 915,103,765 ways, and meet gambler Archie Karas, who arrived in Las Vegas in 1952 with $50. By 1995 he had turned it into $40 million, then lost it all again a year later.

Finally, there are (as so often with books like this) some wonderful explanations of where words come from. 'Stigma' was the ancient Greek name for the identifying mark tattooed on to criminals.

And a signet ring was traditionally used to stamp your seal on documents – the word has the same root as 'signature'.

Winston Churchill's ring bore his family symbol (the Spencer griffin and the Churchill lion), while the one worn by our current king is 175 years old and was given to him by his mother when she invested him as the Prince of Wales.

It bears the words that form the motto of that office, 'ich dien' – meaning 'I serve'.