I haven't read the book. I thought the plot was easy to follow and exciting enough. I don't know what really needed a more thorough explanation. I mean, the Butlerian Jihad certainly sounds interesting, but now that I know about it, my opinion or understanding of the plot hasn't really changed.

In general I'm not a fan of the type of movie where everyone knows there's going to be a sequel so the emotional climax of the movie is closer to the middle and there's not too much suspense towards the end. So, overall, I just thought the ending was pretty dull.