This book is a spin-off of "The River" series. I read this after finishing "The River" series so there were some references to the characters in them that had me a bit confused, but I won't go into that to avoid spoilers. I recommend reading this book after "Devil's Throat", which is the 6th book in "The River" series, in order to keep the parallel stories straight." Blood Oath, Blood River" is a stand-alone book but I recommend starting with "The River" series first so you understand everything that they're referring to concerning being "gifted" and being in "the river".
I enjoyed this story about Deem and Winn and learning more about the Mormon culture. Deem is a gifted woman of about 20 years old and Winn, also gifted, is her male friend who's a bit older than her. They aren't romantically involved, not for Winn's lack of trying, but Deem is put off with his free-loving ways. It's fun to see them kid around each other and Winn trying to coax her into his bed, to no avail.
This story centered around Deem trying to find her deceaced father's journals, which she's sure would help her develope her "gift" . She's sure that her father's friend and confidant, Dayton, has them or knows where they are. These journals are usually passed from generation to generation with each subsequent generation adding to it with their experiences with the supernatural. She makes some friends and some enemes in her quest alongside Winn. You really feel like you're there with them and can relate to Deems struggle to locate the journals and her (SPOILER ALERT) anguish when her friend, Claude, gets murdered by Danites, a vigilante Mormon group who do the higher-ups dirty work. The characters are well developed and I found very few editing errors. If you enjoy a light-hearted novel in the supernatural genre, you'll enjoy this. I've swapped another novel for "The Impossible Coin", the second book in the Downwinders series in my kindleunlimited so I can find out if Deem ever finds her father's journals and what's inside the boxes she finds that Dayton was trying to get when he murdered Claude.