The Science of Pleasure by Jacquelyn Frank

In the Name of Science
Dr. Jenesis DeBruehl once hoped that her scientific research would have positive ramifications for humanity, only to have her work twisted by the evil Dr. Eric Paulson and used to torture innocents.
Seven years later she finally has her own lab again, despite her checkered past. Kincaid “Kin” Gregory is a Morphate, one of the people mutated by Paulson. Now running the lab that Jenesis is joining, Kin is surprised by the lust he feels for the human woman. While Jenesis struggles with her guilt over the role she played in Kincaid’s mutation, he encourages her to use him as her personal test subject. No limitations. With Kin’s body all hers, Jenesis is about to make a whole new kind of discovery . . .