From MPR news:
"Firefly Hollow": The children's book that began with a painting
In the publishing process, children's books typically begin with a story — then the illustrations follow. But that's not how "Firefly Hollow" came to be.
Writer Alison McGhee, who has published several books for both children and adults, received a package on her doorstop six years ago. Inside were full-color paintings of entrancing creatures: A mouse-like character in a sailor's outfit and a cricket curled up with a cup of tea. The illustrated companions were adrift in a small boat, sailing down the river....
listen to the full interview here