This is not at all what I expected, even though on reading back, it is exactly as described in the blurb. For some reason I got it into my head that it was a fantasy! 
Instead, it’s a very stressful exploration of two deeply flawed people and their families as they prepare to get married. The whole way through I just wanted them to TALK to each other and go get therapy. 
There’s some quite graphic medical content that I wasn’t expecting either, even though it literally said on the back that one of the main characters is researching traumatic brain injuries. It was really interesting, but not a relaxing holiday read at all.