It's possible you're thinking of a fictional work, perhaps a book, movie, or TV show. Could you provide me with more context about where you encountered this phrase?
For example, tell me:
* What kind of story are you interested in? Is it a mystery, a thriller, or something else?
* Where did you hear about this Black Book? Was it in a book, a movie, or a TV show?
* What kind of secrets do you imagine being in the Black Book?
Knowing more about your interests will help me understand what you're looking for and potentially provide you with more helpful information.