The best book I've read about the stranglings is "The Boston Stranglers - by Susan Kelly.
It really goes into detail about the crime scenes. I didn't know several of the women were stabbed.
One victim, Patricia Bissette (not sure of correct spelling) was pregnant, was in her bed and covered with her blankets, not displayed. I believe she was having an affair with her boss and was supposed to testify in some kind of trial.
I read this book when it first came out so am a little vague on some of the details, but was very surprised that this was even considered a Strangler victim. Sounded more as if it was someone close to her.
The author believes there were several different killers, and the police were looking at different people until they all got lumped together under "The Boston Strangler.