I've read the book this film is based on, and while I realize print and film are two very different mediums and what works in the former won't necessarily translate to the latter, there is something to be said for trying to preserve the coherence of the original book if possible. That didn't happen with this film, I don't think.
That may have something to do with the director, Bong Joon-Ho, and his instincts for social satire, which were ramped waaaaaaayyyy up in this movie. Well, he did pay for the rights, and he can write his film however he wishes. The question is, is this a good movie in and of itself, or in comparison with the book?
I'm not sure it is, by either metric.
First, to enumerate the good things: Robert Pattinson is excellent in this film. He plays against himself in portraying both characters--the sweet, earnest, dimbulb Mickey 17 and the murderous, assholish Mickey 18--and pulls off both characterizations. (The director added ten more clone-deaths to the total, for no reason that I could see, given the book is called Mickey 7.) Steven Yeun is also good as Mickey's "best friend" Berto--Timo here (although I wish Mickey's punching Berto out at the end had been kept from the book). Naomi Ackles was okay as Nasha, even if she wasn't given all that much to do, and the director definitely pulled his punches with the three-way sex scene.
And then there's Mark Ruffalo and Toni Collette.
Look, those are two fine actors, especially Toni Collette. The problem, for me at least, is why they're there. Kenneth Marshall was the commander in the book, but he definitely wasn't this failed former Senator and thinly disguised Trump clone (which maybe isn't fair, as this movie was obviously filmed long before the election). Their whole over-the-top storyline of husband-and-wife cult leaders colonizing a "pure white" planet (which made me wonder how the African Nasha and the Asian Timo even made it on board the ship in the first place) was a very ill-fitting and clumsy slather over a straightforward sci-fi first contact story.
Which would be fine if the satire was worth the extra slather. However, I don't think it was. Toni Colette's character is obsessed with making "sauce" for her dinners, and ends up chopping an alien appendage to do so. This is not only disgusting, it's dangerous--I mean, let's chow down some alien DNA without investigating what it's going to do to the human body, why don't we! Meanwhile, Senator Marshall is trying to con sweet-talk his colonists into starving themselves and practicing abstinence to make the colony work (a bit of business that had way more play in the book, but which is pretty much glossed over here). In the final confrontation with the alien pillbugs called the Creepers, Marshall leaves the colony ship to meet the leader and gets blown to smithereens by Mickey 18, attempting to stop the imminent war between the species. Again, this is not what happened in the book--Marshall is alive at the end of the novel, and Mickey pulled off the con of making him think the Creepers had taken the nuclear bomb that was supposed to end them, to force a detente between humans and Creepers. And in the book, there was nary a chopped-off Creeper tentacle to be found.
So it sounds like I'm saying "read the book, don't bother with the movie." Well, from a science-fiction viewpoint I am saying that. I think this would have been a far better film if the original plot points of the two Mickeys struggling to hide themselves and both suffering from starvation, and the escalating tensions between humans and Creepers, had been more closely adhered to. At the same time, I know many people love Boon Jong-ho's commentary on classism and capitalism in his films and his instinct for social satire.
In this case, this makes the book and movie Mickey 7 (and again, the extra 10 Mickey deaths were simply unnecessary) two very different animals. Overall, this is probably something that Snowpiercer did better (while spawning a very good TV series to boot). Robert Pattinson's excellence in the title role notwithstanding, this film fell a little flat for me. But if you like black comedy and your satire very over-the-top, you probably will enjoy this.