Simak has dealt with a large number of themes: aliens, pantropy, travel to the stars, immortality, time travel, alternate worlds, etc. However, common to most of his books is the pastoral or American small-town viewpoint--Simak was born and raised in Wisconsin, and the way his plots are built around an (often many-layered) enigma. The former is explicit in his most famous book, City, which tells of mankind's abandonment of cities and eventually earth in a return to a pastoral lifestyle, leaving them to robots and intelligent dogs. The Werewolf Principle is an example of the latter [Neal (who ought to know anyway): a better example is Ring Around the Sun, but it is not as good a book!]. The protagonist is found in space in suspended animation with no memories except 200-year-old general knowledge, but the ability to change into alien forms. The story is based around his discovery of who--and what--he is, and what his purpose should be.
Way Station tells of a man, born before the American Civil War, who by virtue of living in a sparcely populated area of the American mid-west has kept his longevity a secret. His house is a way station for alien teleport travellers between the stars. The station keeper has, over the years, absorbed many alien values. When finally called upon to chose between humanity and the stars, his conflict is typical of Simak.
M.H. Zool