3.5 stars. Not your usual Rachel Caine book. Devil’s Due is the second book in Rachel Caine’s Red Letter Days series. If you’ve read and loved Rachel Caine’s other books, be prepared for something completely different. The Red Letter Days series is more like a conspiracy thriller with a touch – and I mean touch – of the paranormal. No vampires, zombies, nor djinn in this series. Devil’s Due starts off slowly, especially if you are expecting a regular urban fantasy or paranormal book. It’s more cerebral. Devil’s Due has an intriguing premise. There are two corporations that orchestrate events that occur in the world. The Cross Society works against the Eidolon Corporation. In the previous book, Devil’s Bargain our heroines Jazz Callendar and Lucia Garza are brought together and ordered to form a detective agency by the Cross Society. They are free to conduct business as they see fit with the caveat that when they receive a Red Letter, they are required to give the letter priority. This book focuses on Lucia and reveals here intriguing spy background. Lucia’s past is very shady black ops style, and some of her past contacts make an appearance in this novel, giving this book more of a spy thriller feel. There are a lot of shifty characters and nothing is really as it seems. For fans of Ms. Caine’s Revivalist series, the Red Letter Days series introduces Manny and Pansy. More of Manny’s background is revealed and it is truly horrific, reminiscent of a CSI episode. I would recommend this series to readers who enjoy conspiracy thrillers and police procedurals with just a touch of the paranormal. For fans of Ms. Caine’s Revivalist series, this book is a must read and will help pass the time until the Terminated is published in August.Thank you to NetGalley and Harlequin for a review copy of this book. Review posted on Badass Book Reviews.