Talk with the book itself.
A small, considered library. Each book answers in its own voice, cites its own pages, and refuses to invent what it does not contain.
In the book's voice
Each book speaks for itself. Narrator or Author. The voice is restrained, exact, never theatrical.
Cited to the page
Every answer ends with the chapter or page it came from. Honesty over fluency.
A book of its word
If a book does not address a question, it says so. It will not invent a fact it does not contain.