Thay movie was awful. As a huge fan of the series, I don't know how anyone can watch it and understand the plot without being familiar with it beforehand.
The BBC series is much better, and goes up to Book 3 iirc.
Yeah the way I see it is that even Douglas himself didn't quite have a single vision in his mind about the story, which is why there are so many iterations (radio, book, movie, tv series, musical? Am I forgetting anything?)
I'm surprised it's never been made into a decent TV show. The entire thing has already been made into half-hour radio shows, so the scripts are there and road tested. It's basically halfway done already.