The Dragon Quartet, Volume 1: The Book of Earth, The Book of Water

Here's an exciting fantasy tetralogy with all the right ingredients: four elemental dragons (Earth, Air, Fire, and Water), each with a human companion. This series takes us from medieval Europe to the distant future, as the world is caught in a war between the forces of greed and fanaticism on the one hand, and the dragons and their guides and allies who seek to restore the proper natural balance to the planet on the other. This volume contains the first two of the four novels.