Vigorous characterization, a neatly tailored plot, and a sense of foreboding that rises with the accelerating pace of the story telling—all these are the hallmarks of a successful thriller. Rachel [protagonist of Summer of Fear], almost sixteen that June, was totally at peace with her responsive, loving family and with her boy-next-door romance. A long, happy summer stretched ahead. Then came the news that an aunt and an uncle had been killed in a mysterious single-car accident and that her seventeen-year-old cousin Julia—whom she didn't know—was coming to live with them. From a remote part of the Ozarks she came, a curiously mature-looking, ungrieving, inscrutable girl who immediately seemed to cast a spell over almost everyone…. Kindly old Professor Jarvis, an authority on the folklore of witchcraft, became [Rachel's] refuge; seriously he told her that the magic of modern witches was the "'the utilization of the mind force to make things happen as they are desired.'" Finally, when the professor, without warning, suffered a stroke. Rachel was certain that Julia was evil incarnate; and in a fearsome climax she managed to head off total disaster.
Ethel L. Heins, in her review of "Summer of Fear," in The Horn Book Magazine (copyright © 1977 by the Horn Book, Inc., Boston), Vol. LIII. No. 2, April, 1977, p. 167.