The Secret wasn't quite as good as The Quest in my opinion. The story ventured from the Lark/Raven perspective that was the set up of the first book, so now the story is following four characters instead of just the two. I think it might have been a bit stronger if it had stuck to Raven and Lark, but it was a break that was needed to set up more exposition. So, I can forgive it that.
You get to learn more about the royal family and the Ariane in this novella, which was interesting. Nearly the entire book was focused on politics: between the kingdom and the Var, between Raven and the people, and between Lark and the other Ariane.
I was surprised by what Raven ended up deciding, although I suppose I really shouldn't have been surprised. It makes sense. I hate the cliffhanger that it ended on, though!
And now, I'm starting on the third one...after which I'll have to wait for the second half of the series to be published.