It is not Gordon Dickson nor William Gibson. I got a paperback book from the library in 1987 or 1988 and then returned it. It was a great story and I have been looking for the author and or title ever since. It is a post apocalyptical setting. The "Necromancers" are two assassins, they kill with their hands, electrical whips that are part of their bodies and extreme athleticism. They are unisex/bisex who love each other and have alien type sex with each other? The good guys are trying to catch the assassins before they kill the important person or persons. The good guys work for some royalty type government.(king, queen and prince/princess) The government is underground or maybe in old subway tunnels?