This book is good enough that you can see why Victoria Holt remains a big name in gothic romances decades after writing this. There are a lot of interesting twists--many characters turn out not as they seem at first, and few are purely good or purely evil, but an interesting mix of the two. The plot did not develop the way I initially expected it to, and I really enjoyed the book because of that.
However, I give the book four stars rather than five because I found it WAY too long--it plods slowly from one plot development to another, expecially in the middle of the book. I did something I hardly ever do--skipped ahead to skim through the slow plot developments and get to the chase, so to speak. This book could have been edited down to about half its length and not really miss anything. After skipping ahead, I did go back and read the book thoroughly to make sure I hadn't missed anything. (I hadn't.)