I really struggled with the third book in this series, written by Andre Norton, but I love Julian May's writing and this book didn't let me down. Visual, fast paced, and with an intriguing plot, I was once more drawn back into the world of the Black Trillium after being kicked out of it by Norton.
What I will say is that if you read the first book, the one written by Norton, May and Zimmer Bradley, then take the individual sequels by those authors as different/alternative endings for the series. Norton's work, Golden Trillium, takes the plot and Kadiya's character in one direction; May's works, Blood Trillium and Sky Trillium, are truer to the original cowritten debut; and Lady of the Trillium by Marion Zimmer Bradley is another path the story and characters can take.
Personally, I like May's creation and how it leads from the first book, but I'll always hold a soft spot for Zimmer Bradley's Lady of the Trillium, as it was the first one I read as a child and the one that sparked my love of fantasy.
So, in summary, this book (Sky Trillium) is good old fashioned war and magic fantasy, but the series as a whole separates into three strands once the authors develop their sequels, which is a bit disappointing and jarring. I would have loved for them to have at least pinned down the general plot and character arcs before writing their own sequels, but that's just me!