I stayed up late to finish this, so it has that going for it. It's a great little (well, it's actually rather long) tale, and for the most part well-told. My main pet peeves were with obvious plot twists and obvious structural analogies.
First, it's a mystery, and Morton does a great job stringing out that mystery by flipping between three different timelines, so you get ever closer to the answers as you progress.
Second, it's about women, and pretty much only women. Mothers, daughters, grandaughters, cousins, you name it. There's usually a pairing of women - a cousin with a cousin, a mother with a daughter, etc. - throughout the novel. This is where her structure tended to annoy me - oh, look, another set of women who work well or don't work well together. We get it.
Third, unfortunately, what she bases her entire story on is a few extremely tried-n-true plot devices. You see them coming a mile off - and while the story is still entertaining (she is a decent descriptive writer, after all) - there's little to no impact when they are revealed.
Fourth, I loved the setting. I want a cottage on an English seaside cliff with a hidden garden. As if I didn't want one before. But her flowery description of this one made the idea even more enticing.