I know I am in the minority here but Keystone just didn't work for me. I thought the premise was fantastic and I really liked the different characters and their abilities. It had all the makings for a great book but the story and writing just didn't measure up. There were a few really good parts but overall, it was just so so and I found myself bored too many times. I even ended up skimming several pages later in the book. 
 I felt the passion between Raven and Christian. I really liked Niko and Gem and Viktor was great too. Actually, I think Niko is probably my favorite character in the book. I am curious what will become of these characters and where their story will lead but I'm waving my white flag and admitting defeat. I won't be continuing this series because this book became tedious for me to even finish. 
 Audible: I added the whispersync Audible narration to this Kindle book. I think the narrator did a good job. I found that I actually preferred to listen to this book rather than read it.