umbers are endlessly fascinating, in ways that letters only sometimes are. For as long as I can remember, I've had the habit of adding up the digits in car license plates, continuing to add till I get a single digit. It's called the digital root. While adding, you can use this excellent short cut: every time you come across a 9, or numbers that add to 9 or a multiple of 9, simply ignore it or them. Makes no difference to the result. (Try it).

What's more, this is the basis for any number of even more excellent tricks you can play on your pals. That story, another time. But it's because of number delights like these that I looked forward to reading Num8er My5teries.

I was not disappointed. I was disappointed.

There can never be enough books like this one sets out to be. I say that simply because so many of us are scared of numbers, diffident at best about handling them. That is more than a pity. These people don't know the joys they are missing. But there are also dangers inherent in being an innumerate population, dangers that far more eloquent writers than me have agonised about and tried to remedy (Try John Allen Paulos, for one). Me, I'm worried enough that I'm trying to take my son and a few pals through a series of "Numbers are Fun/Numbers are your Friends" sessions.And that's why I was happy to read this book.

Marcus du Sautoy organizes his material by its connections to various unsolved mathematical problems. That was immediately appealing, because it makes the point that the problems that eminent mathematicians have been unable to solve are not necessarily opaque to the rest of us: we can grasp at least the fundamentals. And the fundamentals are fun. Like: Did you know some poker players can shuffle a deck to apparent perfection, but still be cheating? (So can you, but hey, I'm not suggesting that you cheat). That has something to do with prime numbers. Did you know that in medieval India, musicians searched for ways to combine rhythmic units to form patterns? Doing so, they hit on a series of numbers that also pops up in shells and flowers and fruit. Did you know that there might be parallels between inviting your friends to a party and colouring countries on a map?

These are all in the book. There are various bonuses too. You will also learn why du Sautoy thought he'd like to name his daughters "41" and "43". "[If] Frank Zappa can call his daughters Moon Unit and Diva Thin Muffin Pigeen," he asks sensibly, "why can't my twins be 41 and 43?" Why can't they indeed. This has to do with primes too, in particular the phenomenon of "twin" primes.

Good stuff in here, especially for a number-phile like me. For the -phobes too, if they keep at it instead of tuning out at the first mention of words like "primes" and "numbers".