Much more accessible than his most famous work, Dune, The Santaroga Barrier is still excellent science fiction.
TSB is the story of a small farming town whose residents refuse to purchase anything, except perhaps cars, from "the outside". After the death of two investigators sent to explore this barrier, Dr. Gilbert Dasein, a psychologist, is chosen by a retail conglomerate to complete a market study of the area.
Weary of the apparent danger to outsiders, Dasein agrees to go, partly motivated by the fact that his old college girlfriend is a resident of Santaroga. After narrowly escaping an alarming number of seemingly-plausible accidents and noticing the pattern of the omnipresent "Jaspers" additive in the local food, our good doctor begins to suspect there is more to the Santaroga Barrier than a mild cultural difference.
The (relivately) familiar setting of this book makes it much more attractive to those not familiar with the genre. Highly recommended.