[In the five novelettes of Operation Chaos Poul Anderson] posits an alternate Earth where magic works and is a part of everyday life, as well as of politics, warfare, medicine, the law, and, of course, religion. The hero and heroine have become the objects of special attention by the Adversary, though they seem only perfectly ordinary members of their society—he a werewolf, she a witch….

Poul's magic—his formal magic, that is—is borrowed eclectically from a good many different sources, and he has done a thorough job of making it seem an adjunct to, rather than a denial of, natural law….

In addition [to the speed of the action], the book is well populated and contains a great deal of humor; and—difficult though it is to imagine under these essentially playful circumstances—quite a lot of genuine emotion.

James Blish, "Books: 'Operation Chaos'," in The...