I only killed him once : a Ray Electromatic mystery
(Unknown)

"A Tom Doherty Associates book."

"Another Hollywood night, another job for electric-detective-turned-robotic-hitman Raymond Electromatic. The target is a tall man in a black hat, and while Ray completes his mission successfully, he makes a startling discovery--one he soon forgets when his 24-hour memory tape loops to the end and is replaced with a fresh reel... When a tall man in a black hat arrives in the offices of the Electromatic Detective Agency the next day, Ray has a suspicion he has met this stranger before, although Ray's computerized boss, Ada, is not saying a thing. But their visitor isn't here to hire Ray for a job--he's here to deliver a stark warning. Because time is running out and if Ray and Ada want to survive, they need to do exactly what the man in the black hat says. A man that Raymond Electromatic has already killed"--Amazon.com