Book of Bravery

I'm not of your world, but I had a front-row seat to a little-known drama that nearly brought about your demise. Truth be told, I've actually been wanting to tell you about this saga for some time.
It's a short tale, relatively speaking. It does, though, begin before the birth of Christ. There's a man named Quintus at the heart of it. First, he was a Roman Centurion, that is, until he ended up in China where he learned a thing or two from an old Taoist.
Fast forward to today, and he still walks among you.
You should know what he did through history wasn't done for himself, it was done for you, and it was done in the face of the greatest evil known to mankind.
(A second and improved version of the novel was published in July 2023.)