The aliens subplot in The Abyss was cut for time. Still a good film, but notably choppy and uneven toward the back half IMO.The first example that comes to mind is one that's been discussed on other threads here extensively, Revenge of the Sith. I won't go over it again here, but I appreciate the YouTube video by OSP that introduced me to it.
Another that comes to mind is Orson Scott Card's novelisation of The Abyss, which adds a lot of depth to the aliens, as well as to many of the characters, particularly Lt. Coffey - he feels much more like a tragic antagonist in the novel.
Yes, I remember that.The Return of the Jedi novelization explained where Luke's new green lightsaber came from (deleted scene from the movie), and had a short explanation from Obi-Wan about how Anakin became Vader after falling into a molten pit (dialog either not filmed or cut from the movie).
Pretty much all the Star Wars novelisations improve on the movies.
Surprisingly, so does the Aliens novelisation.
(Same author responsible for quite a few of these! Might add The Black Hole, Krull, etc to the list.)
It restores cut scenes from the movie, covering Ripley’s attempt to pick up her life on Earth, and events in the colony leading up to discovering the aliens. It also develops the characters of the marines more than the movie does.The aliens novelization is better than the Movie!!!
Really?
I haven't read it so I haven't the foggiest, but what reasons would you list that it is better than that masterpiece of cinema?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.