Now, after reading first six books of kushiel's legacy during three weeks, I think this was probably the weakest book in the series. Thing making it worst of the series? On my opinion the fact it has most magic in the set. For a long time I've thought that magic as a major plot element ain't that good idea. Especially in a book based on intrigue. It's problematic because reader knows how the world works, but magic is an endless well from which to draw unexpected plot twists.
Another problem albeit quite small is structure of the books in series. It get's a little repetitive after reading six books in a row during short time. So I recommend keeping reading something else between Phédre and Imriel story arcs.
About the plot I can only say don't be scared of introduction up there. Plot really ain't that simple. Tale of the books 4-6 is a basically a growth story of a boy changing it's focus to love forbidden by politics and old hatreds somewhere around the middle.
But now, to the good thinks about the book. I like Carey's writing style and use of words, although english ain't my native language. I'm learning new words constantly which is actually quite rare. List of characters at the beginning of book is quite long, which is good in a series containing lots of court intrigue and politics. Characters are interesting and their actions are logical most of the time.
In the end I enjoyed reading this book and that's the only thing that matters. First three books were certainly better, but if one compares this to other books in fantasy genre in general it's definately near the top.
I'll elaborate this more at later date.