They Walked Like Men
From Kfir's list on realistic science fiction.
This story of alien invasion is hauntingly realistic and frighteningly fun. It has one of the most original plots I have ever seen and, despite the absurdity of the events recounted in it, this book has a ring of truth to it. You read something utterly preposterous and murmur to yourself, “this might happen!” After reading it, you will start looking at events around you differently.