"The nice thing about quotes is that they give us a nodding acquaintance
with the originator which is often socially impressive."
Kenneth Williams, Acid Drops (1980)
What is an epigraph? It's a short statement (a quotation, an idiom, a poem, etc.) that comes at the beginning of text, but the words are written by a different author who is usually cited after the statement.
I am not a big fan of using famous quotes or epigraphs of any kind in books. Why? Because it doesn't do anything to further your voice as the author. It validates the person you quoted, and usually that's about it.
The worst thing that could ever happen to an author is that you get on a fabulous show, the interviewer reads your book, and during the interview says something like, "You quoted Winston Churchill at the beginning of Chapter 2. Tell us about that."
Now you are in the position of telling the interviewer why you chose the Churchill quote, what it means to you, and how it relates to your book. What will the audience remember? The Churchill quote.
Why not use pull quotes (highlighted text pulled from the main body of the text) from your own insightful prose? You have ideas. You have profound thoughts. You have wisdom. Your words are valuable too, and you are the first one who should honor them. Why not celebrate your own wisdom and talk about that when given the chance? After all, you want that interviewer to say, "Mr. Author, at the beginning of Chapter 2, you said something profound. Tell us about that!"
"Craft your thoughts into such profound wisdom that
future authors will endeavor to quote you in their own books."
Lisa Pelto, CMI-Keyring, 2017