Gail Herman, formerly a children's book editor in New York City, has written picture books, easy-to-reads, and chapter books, including many titles in the Who Was/What Was series. She lives in Newton, Massachusetts with her family.
Somewhere between a level 1 and level 2 reading book, it's basically just a watered down version of the movie. Although I don't think it's all that, my 5 yr old loves the movie and so was excited to be able to read this by himself. So it has some merit, but mostly to get a kid to read, not so much in the story or plot.