I'm not sure specifically as I haven't read it. It could be about a new journey of a sinner, perhaps their path to redemption or a new misdeed they get involved in.
The story of The Sinner mainly focuses on uncovering the hidden motives and past traumas of a seemingly ordinary person who commits a shocking crime out of the blue.
The Sinner isn't based on a true story. It's the product of the writer's imagination and creative storytelling. The drama and events are crafted specifically for the show.