One of the best things about movie tie-in paperbacks, aside from their brevity and probable familiarity with the storyline, is the speculation within them. Did they work from a treatment? An early version of the script? Or the actual movie?
This book dealt with an early version of the script, so it doesn’t actually jibe with the movie that well. In addition to the extra depth that the authors add to the interior lives of the characters that you don’t get out of dialogue, this book has completely different scenes than what appears in the film. Some are missing, too, such as the original beginning scene (Marty with the big guitar amplifier). Ergo, this book is sort of like a weird alternative-universe version of the movie.
An interesting artifact if nothing else.