I have mixed feelings about this one: I had loved In A Dark, Dark Wood and was really excited about this. Several reviews have unfairly said this is ‘just another The Girl on The Train’, which I think is misleading and simplistic; it doesn’t especially rely on the presence of an ‘unreliable narrator’ (which even TGOTT did not invent) and it does not follow a particularly similar plot.
What it is, however, is very similar to one of my favourite Hitchcock films (no spoilers!). For me, this (and possibly having read too many thrillers before) made the solution all too transparent and I suspected who/what/why/how/when as soon as the cruise passengers were introduced.
However, I liked several of the characters, and the story was cleverly plotted. I particularly liked the use of text and email transcripts to break up the different parts of the book, and to foreshadow how the story might pan out. I thought the final scene was a nice touch.