Hellfrost is a Norse campaign setting, think Conan in winter with epic tales. The expanded rules for magic is worth the purchase especially if you want something different in terms of how magic is handle in Savage Worlds. This guide gives a good overview of the world, back history, races, and Gods. The art work is top notch mixing different styles of art to paint the whole picture of the seriousness of the ever growing winter. I would recommend this supplement as it is a quality product.
For monsters you will need the Beastary
For the map of the world and places to explore you will need the Gazeteer.