Are there any major differences between Shoeless Joe (the book) and Field of Dreams (the movie)?

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.