"Elves, Wights, and Trolls" by Kveldulf Gundarsson (http://www.amazon.com/Elves-Wights-T.../dp/0595421652) is a decent book out there. There aren't many good books out there other than the Poetic Edda and Prose Edda, at least not from I'm being told from my fiancé (he's a Heathen).

He says you should look up Spell Singing or seiðr and possibly look into Odin since it's pretty much his domain.

Of course, learning Norse or Norse-based languages and looking into their books might also help out, but those languages are very tricky and not the easiest to learn.