Book excerpt: If you're intrigued by the fact that Jack the Ripper was left-handed, or that Heinz ketchup flows at 0.7 miles per day - and, more importantly, intrigued by why you're intrigued - then this book is required reading. Convinced that our love of trivia must reveal something truly important about us, Mark Mason sets out to discover what that something is. And, in the process, he asks the fundamental questions that keep all trivialists awake at night: Why is it so difficult to forget that Keith Richards was a choirboy at the Queen's coronation when it's so hard to remember what we did last Thursday? Are men more obsessed with trivia than women? Can it be proved that house flies hum in the key of F? Can anything ever really be proved? And the biggest question of them all: is there a perfect fact, and if so what is it?