Christopher Abram's Myths of the Pagan North, I figured it was yet another retelling of the myths, maybe with a little analysis thrown in. Boy, was I wrong. This is a wonderful textual analysis of the various sources of northern lore, from runic inscriptions to skaldic poetry to the more familiar Eddaic poetry and Snorri's Prose Edda. In it, he discusses the pros and cons of each source, giving valuable insights into the timing and motivations for each, and uses specific myths as case studies to demonstrate how different sources treat the same material and how the myths themselves morphed over time in response to changing social conditions.
The chapter on the mythological value of skaldic poetry alone would be worth the price of the book, but his insights into how the stories changed as Christianity became more dominant, and his thoughts on the relevance of the myths to the practice of religion are wonderfully interesting as well.