Clifford Donald Simak 
World That Couldn’t Be [PDF ebook] 

When he sets out on a mission to interact with the humanoid inhabitants of a distant planet in order to put them to work as laborers, Duncan has no idea of the challenges that lie ahead. In addition to the complex task of dealing with his less-than-cooperative charges, the intrepid hero must face down a menacing beast known as the Cytha. Will he make it out alive?