Engrossing, tightly-wound, and interesting. I was going to say it was a short book, but looking, I found it was 262 pages. It's just such a page-turner, it went fast. One of the few books where the tension made me want to skip forward to read the end so I would know! I looked up de Clérambault's syndrome, also called erotomania, and it is a real thing. I sometimes avoid McEwan because his books can be so dark, but while this was a kind of noir thriller, it wasn't as dark as I was worried it might be. He's clearly bucking the trend that every modern novel must have a rape or incest to be taken seriously.