Meh (spoilers)
Thought it was pretty good until the end. (Just stating up front that to me it's pretty obvious that he had only killed his mother and Laura, and that his mother told the truth to Laura about Ramon having sex with male students.)
So, we have a homosexual (why?) who is not a serial killer, but who kills his mother, and then kills his ex-wife in a premeditated and cold-blooded fashion, after mentally torturing her, and then rapes the body, so he's also a necropholiac. And by the way, there's no explination as to how he got to be that way.
In the beginning I thought we would get hints to how this man developed into a psychotic serial killer. Then I thought he wasn't a killer and only wanted revenge for what his wife had done to him - I even thought that maybe the wife would turn out to be the bad person (being the biggest mental torturer so to speak) - that would actually have been interesting.
In the end the story and characters merely served the purpose of getting as many twists in as possible. Believability? Who needs it.