So, I have a lot to say. From a writer's point of view, I admire Casey's writing so much. And just like in Breeder and Archer, Casey writes with beautiful descriptions and imagery throughout Master.
From a plot point of view, I had a really hard time loving where this story ended up. And sometimes that happens with series.
The thing I had the hardest time with was how much internal dialogue was going on with Kate and Ian. I wanted more action and less personal reflection.
However, for how entrenched this story is one's personal conversion to Christianity, the internal reflections made sense.
As for the Christianity plot, I personally don't have any problem with Christian fiction. I'm a Mormon Christian, so I'm very familiar with Christian beliefs. However, I don't like reading Christian fiction because the lessons the characters have to learn or the problems they have to overcome tend to be blatantly obvious to me. So I get impatient with their personal journey. On that same note, I don't like to read Christian fiction for my personal religious teaching. If I want to be preached to, I like to read from the scriptures themselves. That's just my personal preference. Regardless, I admire Casey's personal beliefs and applaud her sharing her personal testimony in her writing.
However, as for the Christianity plot within Master, it was so unexpected because of where I thought the series was headed from reading Breeder and Archer. But maybe I was missing the regions undertones throughout.
So overall, I didn't LOVE Master because I wanted a different ending for Kate and Ian. I admire Kate's desire to dedicate her life to God. But I don't think that meant she had to sacrifice her love for Ian to fulfill that purpose.