Spoilers below: I just finished it and I thought it was utter horseshit, only made initially interesting by the contorted editing. Mind you, I do hate Grand Guignol. By halfway through it was ostentatiously clear that nobody was letting Catherine give even a word of explanation, and that not a single reader who blamed Catherine ever questioned how Nancy could have known all that detail (much less why Nancy was so obsessed with her dead son's sex life). So when Catherine did explain it was obviously going to turn the story on its head. Which it did, in a maximally unconvincing way, yet everyone believed her instantly even though Nancy's story hung together much better. Also, there were warnings about physical, psychological and sexual violence at the start of each episode, but we didn't actually see any (unless we count Bridgeport's stalking) until the last episode, so it was pretty obvious where it was going.
It was choc-ful of "Who would do THAT?" moments, such as when Catherine, especially given her past experiences, (a) thinks she can go around to her crazy stalker's for a nice cup of tea with no thought he might try something, and (b) when she wakes up after he HAS drugged her and doesn't get the hell out of there as fast as she can. Not to mention when young Catherine casually leaves the key in the door of a hotel room in a foreign country. What woman alone for the first time with a child would ever do that? And then, at the end she keeps phoning Robert, who she knows won't answer her calls, but doesn't think to phone the ward. Not to mention that in ICU the nurse patient ratio is 1:2, so they should be watching Nick closely anyway. As for Catherine's "forensic evidence"--what, had that moved house several times with her? Where did she keep it?
At the end, when she tells Robert she's leaving him because he was happier with the version where she was raped than the one where she had pleasure in the affair: surely the main thing all the readers of the book, including Robert, were censuring her for was not intervening in Jonathon's death for selfish reasons? In the version where she was terrorised and Nick threatened with disfigurement, her actions on the beach become understandable instead of murderous. Any husband would be happy about that turn of events. Another thing: if I'm not mistaken, in Nancy's version the pair have an affair for several days in Italy, yet in Catherine's version the day she first sees Jonathon and the day he dies are consecutive. If the latter is the case, then surely Robert, who knows when he left Italy and when Catherine came home, would spot the discrepancy in Nancy's story?
It was very anodyne that Bridgeport simply concluded that Nancy had always covered up for Jonathon and he's therefore repudiating them both--though apart from the dark inferences around the first girlfriend, immediately before Catherine met Jonathon, we were never given any clue to what might have needed covering up. Nancy's obsession with her son, visible in the way she lived after he died and in the story she spun from the photos, strongly suggested child abuse, but I'm not sure Stephen drew that inference, or that we were supposed to. Certainly Jonathon appeared to have inherited sociopathy from both parents.
I thought all the leads gave performances ranging from blameless to impressive, but the characters and script couldn't have been much crappier. I can't imagine the novel was much better, because the whole plot creaks with contrivance.