In Shoeless Joe, the author goes more deeply into the background of Ray Kinsella and his relationship with his father.    In delving into the Kinsella family past we are also introduced to two characters in the book that are not in the movie.  One is Kinsella's twin brother Richard who had been severely estranged from his father when he died.  Ray convinces Richard to come to a "game" and Richard eventually begins to see the game and his relationship with his father is also healed.  The other added character is Eddie Scissons, whom Ray had befriended years before.  He is the man who sold Ray the farm.

Another difference between the movie and the book is a theme of religious experience.  The Christianity of Annie's family and the inhabitiants of Iowa is contrasted with the quasi-religious experience of the Kinsell baseball field.  Christianity is presented as a dry, dead religion which cannot fulfill the desires and emptiness of the lives of the characters in the way that baseball can.  The Christians in the story are humorless and merciless men like Annie's brother Mark, who is trying to steal away the Kinsella farm to make it into a computerized farm. There is no magic in the Christianity Mark and his family practice. This commentary on Christianity is lost in the transition from book to film. 

How does Shoeless Joe differ from Field of Dreams?

Kinsella's novel has some significant differences than the film.  The most obvious is that J.D. Salinger is not present.  Terrence Mann is the author who has become disenchanted with modern life.  It works to an extent, primarily because James Earl Jones is very skilled in bringing life into an author that never existed.  Yet, it rings a bit off in that the audience, even one who has never read Kinsella's work, is expecting Salinger to be present.  At the same time, the presence of "the oldest living Cub," Eddie Scissons, is not in the film.  His character is completely removed from the film.  Richard Kinsella, Ray's twin, is also absent in the film.  This also means that Gypsy, Richard's girlfriend, is also missing.  In terms of thematic content, I don't think that the film is one that emphasizes religion and the spiritual dimension that the book does.  The film depicts the judgmental and self- righteous nature of Annie's parents as more representative of social conformity that Ray's building of the baseball field and his exploits is poised against.  However, I do think that the film and book both do a good job of exploring the idea that the link between father and son is one that can exist through baseball.