This book was an absolute disaster. Maybe I've just been lucky and read some great thrillers, but honestly I don't think this book should be able to be classified as a thriller. The premise was intriguing enough: 5 couples get dropped off on a dreamy tropical island to compete against each other in a reality TV show, but a massive storm sweeps through the island and turns the competition into a fight for survival. Who wouldn't be interested? I was hoping for mystery and psychological suspense (as promised in the book's description) but instead got a highly predictable rip-off of Lord of the Flies with a cast of instagram influencers. (The fact that LOTF, a classic novel, even gets referenced during the climax of the manufactured "tension" really set me off...).
There's so much wrong with this book that it's difficult to know where to start. The characters were all shallow caricature's of what the author assumes that Gen Z/millennial influencers are. She posits our "main character," Lyla, as the "brains" of the book since she's a postdoc scientific researcher, but Lyla ends up being just as superficial and helpless as the rest of the women. Though the book picked up pace towards the middle/end (and mercifully put us out of the misery of the first 30% which was slow as molasses), at no point was I gripped or desperate to know what happened next. I was waiting for the twist that literally never came. If the reveal that happens around 90% of the way in is Ruth Ware's idea of a "twist," I am so glad that I have never picked up her other novels. By the end I literally felt like I had wasted all the hours I put into reading this. 
The only reason it gets 2 stars instead of 1 is that there was some semi-intriguing moments of tension throughout, and I was invested in a few characters and their survival by the end. The writing wasn't terrible, I just wish that the plot was more fleshed out in a way that was at least semi-believable.