Great book... in a word... simply marvelous. Imagine a world were the seasons don't last only three months, but thousands of years, like on the ancient Ice Ages On Earth. And when the Spring comes, it brings a new oportunity for the Freyr's sons (the humans) to take dominance over the Batalix ones (the fagors). These two so dissimilar races battle for ages without really knowing the reason for that conflict. But when the spring comes, it is written, it's time for the humans to prosper and the Fagor gonna be dominated... once more again !
For me, it's a must read, on the highness of Dune. And for a trilogy, the others books of the series are read in a grasp !