4 out of 5 rating for Reign of Winter Adventure Path
Disclaimer: I've only run Book 1 of this AP and don't know if I'll run any of the rest of it. I like the idea of a winter-based campaign - different feel, look, and foundational challenges - and Baba Yaga is an interesting character, as well. I'd bought Book 5, with Rasputin, and was very impressed by the story, encounters, and overall idea after reading that - and was looking forward to getting to it. Anyway, Book 1 starts out with a plausible hook, and presents problems and encounters that flow well from one to the next, eventually bringing the PCs to the climax of the book, and then the knowledge that there is more to come. I went a little easy on the cold weather rules, as they would have really slowed down and harmed the party, and thus would have gotten in the way of the story. I think it's enough to use them as a way to make the players think more about their environmental surroundings, rather than creating a subsystem that creates potentially story-sabotaging stat problems. Overall, it was a good story, made up of encounters, locations, and NPCs that made sense within that story and related to one another.