I look at the book as kind of a "reference text" for the movies, providing background and details you don't have time for on screen.

There is plenty of plot material in the unused chapters to form the basis of additional GF film sequences.

The Jules/Lucy Mancini segment has been rendered totally moot by GF III, so I basically just don't pay any attention to it. It's kinda like a Bobby Ewing Dream Sequence.