3.5 Stars 
 I enjoyed Poison Study very much. It was a fun read and I enjoyed the plot development. Yelena is a smart character with a strong will for survival. I really liked the slow development of Yelena's backstory that occurred as flashbacks triggered by a current event or conversation. She endured so much, but never made apologies or used excuses to justify her actions. Most of all, I loved her compassion and how she tried to put others before herself.