Medicine and magic - The concept got me to download the book. There's solid potential in the idea. Alas, this book feels more like medicine OR magic. Aside from Katie's (useful but inconvenient) knack for knowing when death is imminent, which is a handy tool for an ER doctor, her magic isn't used medically, and she seems to do everything she can to keep her two worlds separate.
Swinging a +20 Stethescope of Power to dispatch demons doesn't count.
The protagonist is a straight out of Boy Who Lived central casting. Magic runs in her family, but there's a dad-shaped hole in her Ancestry.com tree that adds a big question mark to the nature and degree of Dr. Katie's magical mojo. (This may never be answered fully; we're still getting info about Harry Dresden's mom and his own capabilities. In a series, some things are just going to take time to unfold.) Her grandparents are the only family she has in the picture; they're magical, but ... HOW magical? I hear you ask. Be prepared to be patient with these questions, and others. You'll get a glossary's worth of urban fantasy terms like archer, mage, knight, carter, shifter, vamp, demon, council, ley lines, etc. ... but there is no glossary.
There's a natural inclination to compare this to Jim Butcher's Dresden series. Magical people living in an urban setting - some trying to blend in more than others. Big Uglies on the Other Side trying to get here. Uneasy relationships between magical humans, vampires, wolves. a council that's not big on dark magic, which Katie fears she has. She stumbles ever deeper down the rabbit hole, but her ill-understood wellspring of a-different-kind-of magic is there to save her bacon time and again, leveling up as needed until the final boss fight.
The demon is in the details. The details, here, are okay, but not great. The first couple of Dresden novels weren't great either, but there was a lot of personality in the other wizard named Harry. Dr. Katie is, frankly, not that interesting yet, and the Big Bad that attempts to invade the world via Minneapolis just doesn't feel all that menacing. The story has potential, but a lot of it is unrealized. There's less meat on the bones than I wanted. The book could have used another round of editing to make the dialog less stilted and repetitive and catch some grammar and spelling issues.
My interest in this book did not flatline, but the pulse is weak. I do hope things improve in the next book in the series, or i won't be sticking around.