This short book is a sequel to Why do Buses come in Threes
by the same authors, Rob Eastaway and Jeremy Wyndham. It explores the math and numbers behind topics such as elevators, fractals and Sierpinski triangles, chaos and the weather, music, scams, karaoke singers and several others. It's a pretty quick and fun read, and should also appeal to teens. An idea in the book that was particularly cool is the weird and wonderful enclosure of a finite area (like a square), by an infinitely long piece of string.
I bought mine for R69 from a country bookstore, but it's also available here, apparently for even less:http://www.amazon.co.uk/How-Long-Is-Piece-String/dp/1861056257