Invasion of the Body Snatchers

Some alien pods come down from space and take on the shape of living things. They typically spend a few years taking over a planet, then zoom off to conquer another areas. They are initially discovered by some people in Marin county who find their relatives are acting a little "different". (The aliens don't show strong emotions.) Eventually, people manage to light fires and do other ruckus to scare them back in to space, thus saving the earth. (Though people still question whether this was a real event or just a psychological hysteria.)

It sounds like a great B-movie. And it has already produced one and its remake.

Many of the plot elements seem familiar. Perhaps this is a testament of the books influence, since many of the other works were written well after this books 1955 release. I had initially suspected it was written in the 70s (due in part to the mention of the 70s dates and familiarity of some of the deices.) However, the repeated mentions of "chesterfields" and doctors that make house calls placed in its proper time period.