De Palma rips off the structure of Psycho - we introduce the protagonist, a frustrated woman unhappy with her life, who starts off on a story that we think the film is going to be about, then she's shockingly killed by a woman, and the film becomes about investigating the murder, and it turns out the killer is actually a man dressed as a woman.
Has to be said though the rip off works very well - it was one of De Palma's most popular movies and a big hit at the box office. It was also controversial at the time because of all the sex and violence - even now, reading it in script form, it remains shocking. The murder of Kate is described particularly graphically with the killer cutting up between her legs while she's still alive.
De Palma has a real genius at creating suspense by distracting the reader's (viewer's) eye - we are caught up with Kate's dilemma (finds out casual sex guy gave her an STI, has to go back to get ring) when she's stabbed to death; we worry about Liz being chased by the killer... then some hoods... then the killer again. Liz is saved twice but both times are set up - Peter, Kate's son (a likeable hero... he and Liz are a good team) and the undercover policewoman (a neat twist).
I wasn't wild about the Carrie like trick ending. De Palma has an interesting writing style - lots of short sentences and paragraphs. He uses a lot of inaccessible big print, which is normally a no-no but I guess as he's the director it matters less.
It's a politically problematic film, with it's violence against women and transphobic nature... but it is well done. The structure is solid.