Amazon.com (ISBN 0312858000, Hardcover)

In the future, humanity has developed five distinct sexes due to the effects of a drug that allows faster-than-light travel. The Concorde worlds have officially recognized all five sexes, but on the isolated planet Hara those in between male and female are considered mutations who must choose to live as one of the two traditional sexes. When Hara regains contact with the Concorde worlds, it's an opportunity for Warreven--a "herm"--to break the long-standing role society has forced on him. But it will also put him in the center of a political battle that will span the stars. Shadow Man won the 1996 Lambda Award.