I will be honest, the first time I read this, I didn't like it at all. I was about to give it to a charity shop when I read it again and was blown away.
The problem was, when I bought it I was in the mood for a sword and sorcery book - we can't read high art all the time, and I just wanted to read a nice, straight-forward hack n slay story. I had read a SF book by the author, saw the cover, and bought it on spec.
However, this book is not a straight-foward story. It focuses on the struggle the main protagonist has with doing his duty in avenging his father, and his attraction to magic and the Earth goddess of an 'inferior' people who his people have conquered. Add in the dreamlike affects of the magic as he learns to use it, and it is actually a complex book.
I don't think the cover does this any favours (my copy was published in 1980). It mislead me into expecting one type of novel when it was something very different. It felt more like a Tanith Lee book (who I also like) than the Conan pastiche I thought it would be. One of the better stand-alone fantasy novels I've read for a long time, shows you don't need an endless series of doorstoppers to tell a good story.