For Magnus Chase: Hotel Valhalla Guide to the Norse Worlds will whet readers' appetites for The Hammer of Thor.
It is a 176-page, smaller format book with black-and-white illustrations throughout. Helgi - the hotel manager - created this book for each hotel guest, so that he wouldn't have to answer so many questions at the front desk.
It has short entries about the deities, mythical beings, and fantastic creatures from the nine Norse worlds, and also contains bonus material, including interviews, newspaper articles, short stories and more. The tone is humorous, complementing Rick's series.