I picked up this title at a used bookstore for a few dollars, but after reading it would gladly have paid the full price for a new copy. "Elves, Trolls, and Wights" is essentially a grimoire and field guide of otherworldly spirits in the Norse tradition. Gundarsson is an academic with a Ph.D. in Old Norse and his writing style reflects this, however, unlike other academic books, "Elves, Trolls, and Wights" is counterbalanced with the author's own direct experiences and practices with the differing spirits he speaks of. Alongside historical accounts of interactions with dwarves, elves, and trolls are Gundarsson's own tales which alone are worth wading through paragraphs of etymology and history. This book is a Pagan's dream -a reliable and in-depth academic book on genius loci written by an actual practitioner for other magical practitioners!
As a field guide, the chapters of this work divide the spirits into types: earth-wights, water-wights, etins, light and dark alfs, dwarves, and changelings. As a practical guide "Elves, Wights, and Trolls" covers herbs associated with these spirits and how they are used (including some I've never read of anywhere else), includes a chapter of rituals for summoning, seeing, protecting from, and working with these spirits, as well as instructions for crafting and using ritual tools and rune staves for spirit work.
If you follow a Norse-influenced path this book is an amazing resource that will get you out of your arm chair practicing magic and working with spirits. If you follow a different spirituality then this book can provide useful ideas on how to work with spirits in your own tradition. Either way, "Elves, Wights, and Trolls" is a very informational and enjoyable read that can be both reference book and practical guide. After reading it you will feel like you took a University lecture on the subject as well as sat down with a Pagan Elder with years of experience.