The Sinclairs are tall, beautiful, and athletic. They are old money Democrats, and they spend their summers on Beechwood island. They are liars. 
 This was a particularly interesting read for me because, like Gat, I have spent several summers with a similar family in their "summer compound." I'm the same age as the cousins, and we get along well, but I'm still conspicuously not a cousin (not that they've ever done anything to alienate me - it's just that they have a history with each other that I don't share). Lockhart did a fantastic job of capturing the sense of idyll, those summer friendships, the surreal bliss of spending all summer reading books in a hammock stretched over the water, as well as how those feelings change as we get older and begin to notice the cracks and politics. 
 The strength of the story is definitely in the characterization - and the island itself is absolutely a character. The downside is the plot. (view spoiler)[The trauma induced amnesia, the characters who are perceived as real but who are actually just figments of the main character's broken mind, etc. It was all fine, but it's just been done so much that I'm not sure it can be saved by even the best execution. As it was, it felt like a cheap way to jerk a few tears for the ending. Ironically, I feel like I would have been far more moved if Cadence's illness were physical, if there had been a real accident (perhaps one that Gat was involved with and felt guilty about), and we saw her being forced to choose between between her love for Gat and her love for her family. Or even if it just explored the grandfather's death and the mix of grief and relief that would come from it. (hide spoiler)] 
 Despite the novel's downside, I did enjoy it. It's a short and relatively easy read (in terms of the mechanics of reading - the plot is, of course, rather brutal), perfect to be consumed whole in an afternoon. Essentially, this is the perfect summer book. It's a solidly written novel with strong characters and a strong sense of place.