This book is set in the THIRDS world which is contemporary America with a twist; fifty years ago there was a virus that caused some of the population to evolve into animal shifters. These people are called Therians, and after much civil unrest there is some level of peace between Humans and Therians. THIRDS is the Human/Therian defense organization that keeps the peace and apprehends rogue Therians, as they are very strong, and THIRDS squadrons are made up of equal numbers of humans and Therians. 
 Calvin and Hobbs are two twenty-fiveish best friends who are also in love with one another. Ethan Hobbs is a large tiger Therian who has Selective Mutism and crippling social anxiety. He is the youngest of three sons, and his father suffers a Therian-virus-related pain disorder. Watching his father suffer seemed to trigger Ethan's mutism. Some of his own family haven't heard his voice aloud in twenty years... 
 Calvin is human, and one of the only people that Ethan is able to regularly speak with, and even then only in close company, and still--only sometimes. They are partners in THIRDS and live together. Calvin has always loved Ethan, as a best friend, and later as a lover, but never told Ethan until recently--when Ethan was critically injured on a mission. It's been several months, and Ethan's not sure what to do. He returns Calvin's feelings, but he struggles to convey his love, being hampered by both his mutism and his anxiety. It was so poignant to be in Ethan's head, feeling his exasperation with himself, and wishing he could be a better (loving) partner to Cal. His eyes are opened in a new way while they sort things out--Ethan gets the full scope of the suffering Cal has endured by remaining his steadfast friend--some of which was intense bullying by humans at their low-income, low-quality high school. 
 Cal is a great guy, and partner, to Ethan, and makes his needs and wants, as normal and small as they may seem, known. It is Ethan who commits himself to bridging the gap. Working tirelessly, Ethan begins to expand his group of people with whom he can speak. It was so rewarding for him, and the reader, to observe these progressions. I think this book will certainly appeal to readers who have special needs persons in their lives, as the communication issues Ethan has mirror, to a degree, those present in many kids and adults on the autism spectrum. I loved having such a window into Ethan's condition. 
 The setting of working with THIRDS is interesting always on account of the police aspect. There danger is ever-present, and there is bloodshed in this book. People very close to both Ethan and Hobbs get injured and bad guys must be found. Also, loving must (and does!!) happen. While a new reader to the series may not know the full backstory on every character, there is certainly enough in this book to portray Calving and Ethan's love story and to pique interest for further reading. I'm looking forward to the next one!