Ice Kingdoms is one of the best researched and well designed OSR products that I have encountered, and I have a lot of them. TL/DR - BUY THIS, NOW. It's a great product for an incredible price.
This book is extremely useful for any DM for any system that is d20 or pretty much ANY fantasy RPG system if you want to run a Norse themed campaign. This book documents the gear, the people, the cultures, the norse mythic races, the gods, and the locations in such a detailed and easy to consume manner that you will not help to be sucked into the setting.
This book is good for any PLAYERS that are playing a norse themed campaign also, even if it's not OSR.
Ice Kingdoms Campaign Setting is filled with great black and white fantasy artwork, many maps, charts, and other useful bits besides just the regular text which is well organized. If there is a single minor negative thing to say is that this PDF needs to be hyperlinked and cross referenced better to make it easier to find things, but good old search works most of the time.
At $3 or even less if you buy in the bundle, this 200 page BEAST of a sourcebook is an absolute STEAL, for anyone wanting anything related to norse fantasy gaming.
The bundle is an even better deal, because it comes with bestiary documents as well as some amazing adventures in the setting. This book stand-alone would be good for players not wanting spoilers for the adventures.
5 STARS - Highly recommended, you could definitely spend your money on a lot less in both quality and quantity of content.