4.5 stars. 
 It's very good. Despite it being slightly cliched and somewhat predictable, I really, really, really enjoyed it. The writing is very straight to the point; Snyder did not bother with flair at all, and I'm still not sure whether this is a good thing or not. I didn't mind it, but I suppose the writing style made it lack a little depth (that being said, Poison Study is still so much better than a lot of YA out there). 
 I also really like Valek's character; a book candy without needing to be possessive, crazy or cool and aloof for no reason. I like that he's calculating, sneaky and cautious. Although he turned a little bit corny towards the end, it was still OK in terms of his character. And I love how his feelings (and Yelena's for that matter) do not cloud their judgements. And I thought the progression of their relationship is natural; you would expect those feelings to develop between them. 
 I wish though that Snyder had made this into an adult book. I think storyline-wise, character-wise, this book could have been so much more. Some of the themes discussed in the book are pretty dark, and with an adult audience as a target, she could have gone deeper and explored it a little bit more. It would have been mega epic. 
 But all in all, it's a very good book. A fun quick-read. Lots of characters to love.