Four best friends - Annabelle, Tanya, Esther, and Chloe - are invited to a private island for an all-inclusive hen party. All paid for by Poppy, another
girl they knew from school. Only Poppy wasn't a friend. Poppy was the girl they spent years bullying, tormenting, and essentially ruining her life. Not wanting to say no to the holiday of a lifetime, they all head there together, assuming that Poppy still just wanted to be friends and hoping she had forgotten everything they did to her. But Poppy hasn't, and she's ready to make them pay.

Everything about this book was just perfect. From the very first page, I was hooked, and I couldn't put it down even for a moment. It truly shows just how bullying in our childhood/teens can affect us as adults. Each chapter jumps between the four friends, with entries from teenage Poppy's diary scattered throughout. I did figure out the big twist a while before it was revealed, and I'm so glad it all played out the way I thought it would. My heart genuinely hurt for Poppy, and honestly, I kinda hated the main four girls. 
I really hope there's a follow up to this at some point because the story didn't feel like it was completely finished. 
A must-read for any thriller lover.