Mr. Nobody is an intellectual exercise. It is a puzzle presented to the audience who is expected to follow along as the main character lives parallel lives simultaneously based upon different choices he could have made as a child. If you understand even the slightest amount about Quantum Physics, which is about my level of understanding, then the movie makes perfect sense. On the level of the sub microscopic, individual particles can live parallel lives where they can be in multiple places at once and the outcome of events depend upon both probability and how those events are observed. How you observe an event after it happened can actually change what happened. At the macroscopic level we don't normally see this weirdness, and therefor this weirdness defies all notions of common sense, but the evidence shows that this is actually how the universe works. A few people smarter than me think that the universe is a self replicating fractal creating parallel universes, so that every possible event that could happen actually does happen in a different universe.
The movie uses people to illustrate some pretty advanced concepts in physics without explaining that this is what it is doing. I knew that is what is was doing when the movie briefly asks why does time only flow in one direction? The movie answers the question by using every day examples to illustrate the concept of entropy, which is how disorder always increases in a closed system, although the movie never mentions the term. You see, according to some people who ought to know, the reason why time only flows in one direction is because of entropy.
The movie seems to hit every concept that I informally learned about physics over the last few years. Even the tagline "If you never make a choice, anything is possible" refers to Schrödinger's cat. This is deep stuff.
Never mind. To the casual observer the movie is designed to be a fable about how different choices in our lives could lead to different outcomes. Well, duh.
In the year 2095 at the age of 120, a man known only as Mr. Nobody is the last mortal person on earth and he is dying. Everybody else on the planet has had their telomeres adjusted to become immortal. Why Mr. Nobody hasn't had his telomeres adjusted is not explained. At the end of his life he reflects on the choices he has made, although it is not clear which choices he made. It appears as if he made many different choices and lived many different lives. Or is it just his failing memory playing tricks on him?
Is the movie engaging? It is. It is also brilliant, but movies like this that are a little too deep and surreal run the risk of losing the audience. Whether you like this movie depends upon how much you like to be challenged by what you are watching.