I must admit to reading this without reading Golden Witchbreed first, but there seemed to be very little problem in that respect - it is set years later, and enough of the past is explained to prevent the reader from losing their way. I greatly enjoyed this book. Yes, the ending is depressing, but I think it very courageous of Mary Gentle not to glue on a happy ending. It's completely believable, in light of what's happening, though you can't help hoping all through... And that's part of what makes this book so good.
I wasn't so surprised to find darkness in this - the other I'd read before was The Architecture Of Desire. Hardly joyful...
Does it ruin a more hopeful book, knowing what is to come after? It doesn't for me, but for those who think otherwise I'd say weigh the happiness you got from the first against the wish to know what happens in the next... I found this an excellent book, not so good as Ash: A Secret History, but certainly something I'll want to come back to many times, and deserving of its five stars.