I’d be curious to know if this movie is based on amy book in particular. In 2007 for the 50 year anniversary of Robinson’s rookie season Jonathan Eig wrote a book called Opening Day about Robinson’s first season in which he questined some populkar myths concerning Robinson such as the Pee Wee Reese story.
The director, Brian Helgeland, also wrote the screenplay. I don’t know what his source material was.