I really enjoyed Rider at the Gate and will be looking for the sequel. I've enjoyed all of what I've read previously by , and so I was surprised at my reaction when I recently read her Rusalka. But now that I look at her bibliography, I see that I've only read her books that are categorized as science fiction, even when they seemed on the fantasy side to me. I would certainly have categorized Rider as fantasy, since it depends heavily on ESP; but that's the only magic that is present. And to my vague recollection Wave Without a Shore seemed like fantasy as well.'s
But anyway, it was the characters in Rider that had me captured, and the characters in Rusalka that never came to life for me. In a lot of 's stories, the fascinating thing is the way she juxtaposes characters of different species and makes them all more interesting by their contrasts. (And shows us different facets of being human through this lens.) In both these series, all the characters are human (discounting the psychically active horses in Rider. They have tastes and personalities, but only develop goals and plans when allied with a rider.)
Perhaps the difference is that the characters in Rider are actively trying to solve their problems, while the characters in Rusalka are reluctant heroes. Yes, that's certainly a part of it; I've never liked reluctant hero stories, going back to 's Thomas Covenant series, most of which I read in college. While I was reading Rusalka I thought my distaste was also because of the dark air of the story: I'm no fan of horror. But Rider is nearly as dark and brooding. I think the characters' gung-ho attitudes drain the power of the darkness.
Anyway, I'm pleased that I've found another series of books bythat I want to follow up on, and hopefully you'll have learned something about these books whether or not your tastes run along the same lines as mine.