They Walked Like Men is an alien invasion novel. Simak sets up a puzzle where newspaper columnist Parker Graves finds himself confronted with shapeshifting aliens who can inhabit “dolls” that allow them to pass as humans. Another group of aliens enters the fray to take over the Earth, but Parker Graves is torn between trusting them or suspecting they are far worse than the original alien invaders. Clifford D. Simak was once considered the equal of Heinlein and Asimov. Sadly, Simak’s work has drifted into the “forgotten” category despite its excellence.