All Flesh Is Grass1965
by Clifford D. Simak
Millville, USA. A small town like countless others, with people who assume that life as we know it is the only kind of life. If there's anything unusual about the village, it's the strange and beautiful profusion of purple flowers that bloom in nearly everyone's backyard.
To Tupper Tyler, the village idiot, who disappeared into a field of purple blossoms ten years before, they were gentle creatures, the only ones who ever accepted him . . . To Brad Carter, who entered an alternate dimension inhabited by silver-crested men who spoke in music, and primitive, evanescent women, they were a brilliant race looking for a place in the sun ... And to the terror-stricken residents of Millville, they were either an undreamed of link to the future or a frightening, unstoppable force.