I regard [Jack of Shadows] as something of a find for me. Mr Zelazny has written several well-received novels already, but I had never come across him before and I read Jack of Shadows with increasing delight and a sense of satisfaction. I doubt if Mr Zelazny can be, or would want to be, characterised as a particular sort of writer—but for the sake of argument I'll suggest he falls into the imaginative fiction category, somewhere between science fiction and fairy tales. In fact Jack of Shadows opens like a fairy story, with strange names and a sort of poetical prose. And, as with all good fairy stories, we are instantly caught, both by the actual narrative and the charm of the imagination that contrived the tale….
The surface narrative is always fascinating, as Jack (who is a sympathetic character) meets, fights and evades his enemies. No incident is overwritten, but given due weight and power….
Mr Zelazny has projected a world with two sides to it: one, the dayside is always bright and sunny with no night at all; the other, darkside is just that. Dayside is, in essence, the world of science and rational argument and not really a very agreeable place…. Darkside is the world of the supernatural, of spirits and superstition. In a central and crucial dialogue with Morningstar, Jack realises that there are different kinds of truth, and that the same phenomenon can be interpreted in more than one way, and that eternal truth is non-existent….
Jack of Shadows is an assertion of a dark side, of its power and mystery. It has great charm and a nice sense of anachronism as, when among the primeval chaos he has created, Jack moans that he has crushed his last cigarette.
Roger Baker, "Fiction: 'Jack of Shadows'" (© copyright Roger Baker 1973; reprinted with permission), in Books and Bookmen, Vol. 18, No. 9, June, 1973, p. 103.