If you think you don’t have a personal brand, then I’ll let you in on a secret: Whether you realize it or not, your actions, the way you speak, how you hold yourself, where you go, what you do, what you write, and your work itself all come together to present a perceived version of your brand.
I published my first short story when I was 39, and my first novel when I was 45. I would never have been able to write what I wrote without the life experiences that forty-five years had given me.
Is your book creative nonfiction where you're showing "real" events in an entertaining and story-like way? If writing in this literary genre do your homework and make sure you're actually doing nonfiction. It can get a little fuzzy when the truth is stretched too far on the creative side (thus turning it into fiction) but still represented as fact.