Roger Zelazny stated that he wrote Jack of Shadows as a “first draft, no rewrite”, which might account for the occasionally elliptical nature of the narrative. Any lack of cohesion in the plotting is compensated for by the dark majesty of Jack AKA Shadowjack’s world. Zelazny is clearly echoing Jack Vance’s Dying Earth stories here, at least in the weirdness of the creatures and landscapes of the darkside if not in the playful ornateness of Vance’s prose. Jack of Shadows also emphasizes the interplay and conflict between magic and science, and the borderline immortality/superhumanity of its protagonist, themes that would play out in many of Zelazny’s other works such as The Lord of Light and The Chronicles of Amber.
Jack of Shadows was originally serialized in The Magazine of Fantasy & Science Fiction in 1971 and was immediately reprinted in hardcover by Walker & Company, followed by a paperback edition from Signet in 1972. Jack of Shadows was well-received from first release, garnering Hugo and Locus Award nominations in 1972--it did not achieve the lasting popularity of The Chronicles of Amber or many of Zelazny’s other books however, and was out of print for over 25 years until it was recently reprinted by the Chicago Review Press in 2016.
Gary Gygax wrote in issue #2 of The Excellent Prismatic Spray (2001) that Jack Vance’s Cugel the Clever and Zelazny’s Shadowjack were the greatest influences on the Advanced Dungeons & Dragons thief class as described in the The Players Handbook (1978). The thief’s abilities as written though are rather mundane and have a low probability of success for beginning characters. If the thief’s skills are re-imagined as being a quasi-mystical version of Jack’s powers, then even a 10% chance of utterly disappearing into shadows becomes a very powerful ability indeed! Of course, Jack as he appears in Jack of Shadows is not a mere skulking footpad but a magician of unsurpassed power, so it makes sense that he was written up as such in Wizards (1983), part of Mayfair Games’ Role Aids line of unofficial Advanced Dungeons & Dragons supplements.
It’s worth noting that although a thief-type class is considered core to Dungeons & Dragons today, the class was not included in the original 1974 box set and only made its first appearance in the first D&D supplement Greyhawk (1975). In some gaming circles this has kicked off a 40+ year debate over whether the thief deserves to be its own character class or if being a thief is properly a role that all adventurers play….