I didn't know what I was getting into when I started this book and was a bit surprised once I started reading it. What I'd long thought was a novel is more a collection of linked stories. Some characters reappear, and there is a general historical timeline that is stuck to chronologically, but this is not a novel in the sense of having the development of a character (unless Mars itself is the character) over the course of the work.
While Asimov's I, Robot seemed more interested in philosophical ideas about intelligence and ethics, Bradbury's work is more concerned with history. The latter is also more of a stylist, with writing that is memorable for its own sake. The history that Bradbury focuses on seems to me to be one of Earth, and most especially of the New World. The extended metaphor between the settlement of the New World and the settlement of Mars is made explicit more than once.
Bradbury's book begins with a story written from the point of view of a race of Martians. In that story, a woman has visions of men from Earth visiting the planet. And indeed, the next several stories revolve around attempts to explore and colonize the planet, with each little group of Earth men killed off in some way before they can bring back news of a successful landing to the people back on the home planet. But in time, Earthlings eventually establish a foothold, this made possible largely through a disease that wipes out Mars's original inhabitants (ala the American Indians).
Eventually, more and more people come to Mars, and it is increasingly seen as a place for young men to go off to make their fortune. And that is where Bradbury's work takes a dark turn, for as Mars begins to be settled, Earth finds itself enveloped in a world war, and new settlements drop accordingly--indeed, as the Martians disappeared, so it seems that humanity itself also will.