I don't know but I think google bard had access to the book's content as well because it mentioned correctly some characters and some places I didn't mention in my question.
That's exactly what LLMs are good at. Cross-referencing information from across the training data.
The response could contain information that you did not specifically refer to but is relevant and/or related. It doesn't even imply that the LLMs had access to the book's content.
