I think if I had the gift and anointing to write a book..I'd pick a a children's story. I like
@Willie T idea.
Id write a book about the view point of one of the animals in the ark, and then the adventures of what he heard, saw, and what it was like when he came out ..and like Willie said...incorporate many animals friends and acquaintances.
I have a soft spot for children's books. My old dad was 90 when he died and along with his heavy bible study books he always had a children's book on the go to read. He passed that gene on to me!
I still enjoy rereading the Nesbit 's books...and C.S.Lewis books etc
Many children's books like those bridge the gap between child and adult..and have a spread of readership.
The gospel and godly standards can come through in type and shadows in the story. :)
Thats my two cents.