The Morphodite is a novel by M. A.
Foster published in 1981.
The Morphodite is a novel in which a man with no memory is trained to be assassin and given the ability to shape-change.
[1] Greg Costikyan reviewed The Morphodite in Ares Magazine #13 and commented that "The Morphodite is different from what we think of as traditional science fiction because it is a psychological novel, which is something we associate with mainstream fiction; yet it is a novel which attempts to explore unusual ideas, which is the essence of science fiction.
"[1]