Beautiful. I love seeing Mercy as the packs alpha female. She's so GOOD at it! Adam was glorious in this one too. LOVED having his POV in a few chapters. 
 The religiousy stuff would bother me in any other book. But I make allowances for Mercy. And there is right and there is wrong. Mercy is always in the right. 
 I felt like Frost Burned was a little like a reminder of everything that was missing in River Marked. Now, I loved River Marked too. But we didn't have the pack. Didn't have Kyle and Zee and Jesse and Stephen much. We didn't have the TriCities or the Rabbit or ANY of the stuff that is part of the first five books. River Marked was great, but Frost Burned is back to what we know and love in this series. The characters are so real to me. I love them. I want every character to be in every book. And I do NOT want to wait another eternity until the next one! 
 Of course, there's only one more really big thing that could happen to Adam and Mercy (exactly how many times are they going to be kidnapped and rescued by each other anyway?), and that's getting pregnant. The series really ought to end on that. A happy safe family. How that could be accomplished considering they're always in trouble with someone? Not sure. The Fae will surely do something in the next book...they can't be expected to stay on those reservations for long. It's retaliation time. And Marsilia will always want Mercy dead. And if she has a baby? They'll want the baby dead too. So...yeah. That could be the last book. 
 Until then...luckily I always have the series to read and reread and reread again. :)