4.5 stars. I did read this in just over 24 hours, but I didn't enjoy it as much as Poison Study. I still loved Yelena, and liked finding out more about her family, her past, and her powers. I felt like she did get kidnapped a little too much, and the whole idea of it began to get a little boring. She'd get kidnapped, then escape, and then the whole thing would happen again. There were a few plot twists in this book and I didn't guess any of them, but again there just wasn't as much excitement as there was in Poison Study for me. However, I still really enjoyed the book, struggled to put it down, and am excited to begin the next one!