Spoilers toward the end.
I read this first when I was about fifteen. My grandmother was reading it, knew I was writing, and suggested I read it for the language, and also because I was very interested in history.
I read the book at least a dozen times in my teen years, and fiercely desired to be able to write that kind of prose. I love rich characterizations, and though I have seen people complain that it starts too slowly, I find that beginning very important.
Is it now unfashionable to love words, to like to read authors who use words beautifully and descriptively? I don't know, but I am only concerned with what I enjoy as a reader, not with trends and fads. I still find this book has much to teach me. English is a beautiful language, and I want to read it used with depth, with lushness.
While Pargetter may romanticize her characters, her 12th century England is not so written. It is brutal for the villeins, and deeply unfair. She shows that that the nobility had almost complete control over those under them, and very few people would interfere. That is a recurring theme in this book, and also crops up in her Cadfael series. (Tangentially, while Pargetter, writing as Ellis Peter's wrote lovely Cadfael novels, I think of those as her eveningtide books; there is far more passion apparent in The Heaven Tree trilogy).
As the story moves on, introducing Isambard (a wonderfully explored character, I think) we can see that there is going to be a clash of wills and self-destructive pride that will pull the roof down on every-one involved. But true tragedy of the ending, for me, is that genuine love that exists between Harry and Isambard. This was the first book I cried floods of tears over, and when a book touches me that deeply, it is very special. Re-reading it recently, I was pleased when I cried again. I felt as if I were not desensitized to beauty, because there is no gore, no horror, no great violence, no sex in this book (all of which I will read without a blink) just exceptional characters, and a grand and poignant story.