Start with high-confidence norse myths books, then narrow by subgenre or adjacent topics.
Otherworld Chronicles #3: the Dragon King
Nils Johnson-Shelton
Orkneyinga Saga
Anonymous, Hermann Pálsson
Mythology
Edith Hamilton, Jim Tierney
The Mythology Book
DK, Various
Sister Bear
Jane Yolen, Linda Graves
Children of Ash and Elm
Neil Price
Arthurian Myths & Legends
J.K. Jackson, Prof Raluca Radulescu
