I think I fall more in love with this series with every book I pick up. It's not *required* to read the previous two books to understand this one, but I'd recommend them. 
 This series revolves around a secret colony of canine shifters--collies, German shepherds, bulldogs, the gamut--who either became "quickened" (able to turn human) after bonding with a special human, or were born "quick" to quickened parents. This colony exists in Mad Creek, California, a tiny mountain town which is fiercely guarded by Sheriff Lance Beaufort, a collie shifter. 
 Jason Kunik is a quickened Malamute geneticist working for a pharma company in Vegas when he got a bad vibe from one of his superiors and learned his personal research (sequencing his own DNA to find clues about quickening) was under direct scrutiny. He fled to Mad Creek, the only home he'd really known, even if he hadn't been back since high school graduation. Anxious to do something worthy of his knowledge and skill, Jason begins interviewing newly quickened humans, to learn if there is a specific pattern to gaining the Spark...and it goes disastrously. Jason isn't a people-person, and he's not a dog person, either. He scares away any of his subjects by being brash and obtuse. *sigh* (Not all scientists act this way!!) 
 Milo was a shelter rescue adopted by the staff at a Fresno hospice, and he's miserable. All the humans he bonds with are dying. Lily Beaufort discovers him while visiting a friend, and dog-naps him back to Mad Creek. Milo's so skittish and in serious emotional pain, only wanting a real home where he's actually wanted. Jason takes pity on him and brings him back to his big cabin, for a few reasons--he finds Milo attractive, he feels a kinship to him as they are both rather misfits, and Jason expects that he'll be able to study Milo's growth into humanity at close range if they live together. 
 They have an unexpected tenderness to their developing friendship. As a care dog, Milo can sense the pain and suffering in others, and even illnesses! He'd been around so many dying people, he developed in a very different way from the "regular" quickened, and that makes him so unique and precious as a subject--but Jason soon finds that he's getting swept away by Milo's tender nature and compassion. 
 This book has a major outside threat: illness. A former Mad Creek resident returns--in his dog form--and he's too sick to shift back to human. Quickened first responders are now becoming ill, and that includes major characters...the backbone of Mad Creek, in essence. Jason, Milo, Tim and Matt (from previous books) are put on the trail to an Arizona shelter where Patient Zero likely had contact with normal, but sick, dogs. I liked how this played out, with Milo and Jason coming to terms with each other, and balancing each other's strengths. Milo seems to love Jason, and Jason's totally afraid to lose his heart to Milo, even if he already has. I really wish we had a little more time in Milo's brain, so we could see how his compassion was only one facet of his affection and growing love for Jason. 
 I'm not a virologist, but I appreciated the actual discussion of the disease, and Jason's attempts to get control of it. He's not a virologist, but as a scientist he has learned the most important lesson out there: admit what you don't know. He seeks help, as surreptitiously as possible, so he won't reveal the colony, but in a way that will gain him the knowledge and expertise necessary to solve the crisis. 
 This book will certainly lead to another, as there is a bit of a cliffhanger regarding Jason and his expertise, but the love story is sweetly completed with Jason and Milo becoming a stronger pair than the two were separately. I really would have liked a little bit more loving in this book--it was nearly 75% before we got ANY real sexytimes, and that was almost too long for me. That said, Milo is the sweetest Labradoodle on the planet, and I'm glad that Jason remembered no human--or canis sapiens--is an island unto oneself. 
 Also of note, I'm keeping a constant observation of my gentle Lab-Pit mix to see if she's got any hint of a Spark happening. *sadly none as yet*