The fourth book of Madeline L’Engle’s Time Quintet, Many Waters, is an amazing look at what the rest of the story of the flood could have been. The quintet is best know for A Wrinkle in Time, but in many ways I think Many Waters is the most remarkable, just for the sense of Biblical wonder L’Engle breeds.
The book is written for children, and it’s a quick read, so you may want to pick a copy up while this story is fresh in your mind.