4 stars because it contained so many themes and stories that he develops much more later. For example, there is definitely a short story predecessor to Fahrenheit in here and some stuff that is reiterated in the Illustrated Man. But, I loved it nonetheless. The approach is interesting, the book is in a semi-narrative group of short stories detailing man's first arrival on Mars and it's subsequent colonization. The story of humanity is told as a whole through different people, a family of Martians, a retiree looking for escape, African-Americans escaping prejudicial treatment in the American south.
I think my favorite short story in here is about the guy who goes crazy from the fourth expedition. He becomes obsessed with preserving the Martian ruins and Mars as a whole from human "civilization" and attempts to kill off his fellow crewmates. Very Twilight Zone-esque. There's another great story in here about a guy who tries to recreate elements of Poe's House of Usher in reality and in defiance of some arrogant thought police.
In short, this is the kind of science fiction I love. Nostalgiac, scientifically false and implausible, but with no limits on flights of fancy or imagination. Bradbury is the best.