Mining the Asteroid Belts

First of all, why is the title of this book about mining Asteroid Belts? When we learned about the Asteroid Belt when studying the Solar System in school there was only one Asteroid Belt. The one in orbit between Mars and Jupiter.
With the discovery of the Trojan Asteroids in Jovian orbit and in orbit ahead and behind of the planet Jupiter, we now have more than one belt of asteroids around the Sun. If we include the Kuiper Belt out beyond Pluto, there are many additional thousands of astero...