Looking for a book simmilar to Jay’s Journal

Hi, I'm looking for a book simmilar to Jay's Journal. Doesn't necessarily need to be a diary and anything except crime novel will be great.

There must be a satanic cult, group, something with satanic theme, not some random magic, and it should be shown from the inside so either as someone who's already in or is yet to join. Also please recommend me something without excessive moralizing, but rather with the character's personal feelings.