I bought this set a while back and have not regretting getting it as I do watch them all. This set consists of the 6 original movies: The Motion Picture, Wrath of Khan, The search for Spock, The Voyage home, and the undiscovered country.
Each movie has what you expect from star trek. The motion picture, Kirk takes over the Enterprise under Captain Decker's command. The second and third movie are a continuation of each other. The voyage home is when the crew of the enterprise go back in time to get whales to bring back to their time to save earth from destruction. The voyage home slightly is a continuation of the wrath of khan and the search for spock. In the voyage home, they were using a klingon ship as that is what they ended up with in the search for spock. The undiscovered country is where the klingons and the federation created peace with each other to become allies.
If you do like star trek, these are the movies to buy. They each have some sort of adventure included with each movie. It does have its share of conflict and that is the makings of a great movie.