Science Fiction; Mystery; Family Drama
Blinded by Science (Fiction)
During Close Encounters' marketing campaign, Steven Spielberg was fond of saying that the film wasn't science fiction but "science speculation," meaning the film was "speculating" on the scientifically plausible. (Source) And while weirder things than UFOs may have happened—like millions of people inexplicably deciding that scaring cats with cucumbers was the best—we're going to disagree and label this one science fiction. Sorry, Mr. Spielberg.
Labels aside, CE3K embodies many traits of its science fiction brethren. But the film is unique in its choice of how to use these genre tropes. Most science fiction films up to that point used extraterrestrials as villains. Invasion of the Body Snatchers and Earth vs. the Flying Saucers (1956) are just two examples of humanity throwing down with these intergalactic antagonists.
Both of these films used the aliens as thinly veiled symbols for America's Cold War enemy, Communism. Close Encounters—released two decades later but still during the Cold War—took this trope, flipped it on its head, and said, "Hey, can't we all just get along?"
Mystery on the UFO Express
Close Encounters is also a mystery, a whodunit but without the murder. From the opening scene, Lacombe and the audience want to know: Who grabbed Flight 19 from the Bermuda Triangle and then returned the planes to the Sonoran Desert with no return address? By the time we get into Roy's story, the obvious answer is extraterrestrials. But that's no more satisfying that saying a murderer did the killing with a weapon in the room. That's the correct answer, but you aren't going to win a game of Clue with it.
The questions of who and why are what propel Roy, Lacombe, and later Jillian to solve the mystery. Who are these aliens? Are they bug-eyed, big-brained conqueror types? The ambassador kind? Or the murderballing insectoid variety?
Also, why are they here? Are they trying to deliver messages of peace? Are they scouts observing the lay of the land before the invading party? Or are they here to collect on the lien the Ancient Egyptians forgot to pay for the pyramids? Do they need our gravel?
The end of the movie answers these questions while still leaving room for interpretation and speculation on what's to come next. But this is the "Genre" section, not "What's Up with the Ending?", so we'll leave the discussion spoiler-free for now.
Taking Sides Against the Family
Finally, there's a fair bit of family drama to be had in CE3K. After his close encounter, Roy seeks out the truth behind his experience, but his wife, Ronnie, would rather forget it and move on.
Enduring less a midlife crisis and more a life-life crisis, Roy grows more eccentric—crying in the shower, sculpting mashed potatoes, and hanging out with Bigfoot believers from the boonies. Tension in the family ramps up and even his children get scared of him. When he decides to trash the kitchen to build a giant-sized sculpture of the mysterious mountain image, the family drama reaches its crescendo, and Ronnie takes the children and leaves.
The odd quality about the family drama in Close Encounters is that it totally lacks resolution. At the end of the second act, Roy tries to reconnect with his absentee family. But when the third act begins, he drives to Wyoming to visit Devils Tower, and his family disappears from the movie never to be heard from again. They simply become a non-issue, which is strange given the amount of time dedicated to them in the first two acts.
Spielberg later mentioned that, had he made the film after he married and had a family of his own, things would have been a whole lot different. (Source)