The Nidaros Book of Shadows is possibly the book of the Nidaros line of Witches. It is unknown if such book exists as it hasn't been mentioned yet. Moreover, it remains unclear if the Nidaros Coven was made up of six blood relatives or if they were a circle composed of friends or such. However, since they were shown to be six Nidaros ghosts, it is more likely they used to be a circle and their coven named itself after the Nidaros because it was their leading Circle family.
At any rate, if such book exists, a list of spells has yet to be determined but since the coven came directly from Europe, it's possible their recorded spells are regional to that continent such as Druidism in England. That would also means, it wouldn't have entries on Voodoo rituals because that magical art is a mix of religions from African and West Indies, that is far away from Europe.