The Puppet Masters
First came the news that a flying saucer had landed in Iowa. Then came the announcement that the whole thing was a hoax. End of story. Case closed.

Except that two agents of the most secret intelligence agency in the U.S. government were on the scene and disappeared without reporting back. Then four more follow up agents also disappeared. So the head of the agency and his two top agents went in and managed to get out with their discovery: an invasion is underway by slug-like aliens who can touch a human and completely control his or her mind. What the humans know, they know. What the slugs want, no matter what, the human will do. And most of Iowa is already under their control.

Sam Cavanaugh was one of the agents who discovered the truth. Unfortunately, that was just before he was taken over by one of the aliens and began working for the invaders, with no will of his own. And he has just learned that a high official in the Treasury Department is now under control of the aliens. Since the Treasury Department includes the Secret Service, which safeguards the President of the United States, control of the entire nation is near at hand.
Science fiction, alien, invasion, Fiction, science fiction, general, Human-alien encounters
Robert A. Heinlein
Robert Anson Heinlein was an American science fiction writer. Often called "the dean of science fiction writers", he was one of the most popular, influential, and controversial authors of the genre. He set a high standard for science and engineering plausibility and helped to raise the genre's standards of literary quality. He was one of the first writers to break into mainstream, general magazines such as The Saturday Evening Post, in the late 1940s, with unvarnished science fiction. He was among the first authors of bestselling, novel-length science fiction in the modern, mass-market era. For many years, Heinlein, Isaac Asimov, and Arthur C. Clarke were known as the "Big Three" of science fiction. ([Source](http://en.wikipedia.org/wiki/Robert_A._Heinlein).)