The Tenant: A Novel of Medical Science Fiction — Charles G. West

Jesse Campbell is a sociopath, horribly disfigured, monstrous in size and wanted for murder. He is spotted on a construction site next to a research hospital in Atlanta, Georgia. Resisting capture, Campbell attacks police, killing one and wounding another. He is mortally wounded with a bullet through the brain.
Dr. Chris Warren, a transplant specialist, researching the transplantation of the human brain, happens upon the scene and attempts to save the wounded monster's life. In the process, Campbell stabs Dr. Warren through the heart with a screwdriver.
Warren's assistant, Dr. John Sumner, is forced to make a desperate decision, and attempts to save Warren's brain by transplanting it into Campbell's body. The operation is a success, but Sumner decides it best to keep it a secret until his patient shows no sign of rejection. Unfortunately, Sumner is killed in a traffic accident, leaving Chris Warren to try to convince his wife, police and hospital staff that he is no longer the sociopathic Jesse Campbell. Wanted by the police for murder, Warren is forced to escape, knowing that no one will believe his wild story.