Can we start with mentioning that cover?! I'd buy this book for the art of the cover alone, it's so captivating.
The comparison to Lord of the Flies intrigued me, and I'm curious to read the book and compare because it doesn't sound terribly similar to LOTF at first glance. I believe the author of Lord of the Flies even joked that the characters were all boys in his novel because girls would have worked together and created a fully functioning society among themselves. I feel there will be a twist in this book similar to Maze Runner, of a party controlling the real life situations the girls face, or at the very least creating them for some "controlled" purpose.
Overall, my first impression of this book is one of excitement! I look forward to reading this book and immersing myself in a story that sounds as if it will be packed with action and suspense and mystery all while developing beautiful friendships between the characters.