The Venus Fix, by M. J. Rose

I couldn't put this book down, its the 3rd in the Butterfield Institute series, but as MJ Rose is a skilful writer its good as a stand alone piece of fiction.
We start with Dr Morgan Snow ,sex therapist and her series of patients. Bob, a patient whose name is even a mystery, is an enigma and has her office swept for listening devices. He admits being addicted to internet porn.
A trainee who performs on the internet to pay for her education and a number of students who she is counselling in regards to their porn website visits.
A performer is murdered in a gory way, with viewers watching. Dr Snow believes along with the detective Noah Jordain (her on/off lover) that the murderer and her patients are linked.
The personal life of Morgan, her ex husband, lover and own teenager make it more real.
Very satisfying thriller I was not sure whodunnit right until the end.