The Black Jewels Trilogy is the sort of book series that it's very easy to get mixed signals about. Some people will tell you they love it; some people will tell you they hate it. While it's impossible to say right from the start which category you will fall into, there are several reasons why you ought to at least give it a try.
Black Jewels is, if nothing else, set in a very unique fantasy world. There are no maps, and in reading, you begin to understand why - the setting isn't in one geographically explicable world, but in three 'Realms', planes of reality that are separate from each other and yet undeniably connected, echoing and shadowing each other. This sort of layout can easily become confusing, but it is presented well enough to understand if you actually pay attention to the text. The world Anne Bishop in which writes is further distinguished by it's underlying belief system - a system which can be summed up by 'Darkness is good' but whose impact is much more subtle than that. This is a world where all women who wield power are witches, where 'coven' hasn't got a bad connotation, and where the majority of the good guys live in Hell.
This is also the world of the Blood, men and woman who are born into power and magic. Their strength is augmented and exemplified by their Jewels - and the darker the Jewel, the stronger the magic. But this is also a world falling slowly into a taint, a taint started centuries in the past, when one long-lived, power-hungry, and undeniably sadistic woman slaughtered any who would oppose her, and seizing power for herself. In the long centuries since then, the rest of the Blood have begun sliding into this shadow, and cruelties of the sort to make a person pale have become commonplace.
It's in this that the greatest danger of a person disliking this series occurs. This is not in any way, shape, or form a book suitable for children, or even some young adults. Other writers who have their characters oppose a great evil may gloss over, or simply ignore, providing proof of just why what they say is evil is - Anne Bishop provides evidence. There is rape, and there is torture, both physical and psychological; there is neglect, child abuse, and gore, and not all of it happens to nice, safe, incidental characters. Characters you know and likely will come to love will be hurt.
So why read it if there's such nastiness? Because a great deal of the genius of this series is that, for all the horrible, awful things, for all the darkness, if you will, there is also a lot of light. There's love, and laughter, and triumphs, as well as the sorrows and pains. There is even, despite the amazing improbability of it under such circumstances, a truly wonderful romance or two. The story is a balance between good and evil, light and dark - a balance made manifest in the central character, the Queen of the Darkness, not merely witch but Witch, dreams made flesh, and the last hope for the world of the Blood to pull itself out of its downward spiral: Jaenelle Angelline.
There's a certain danger to writing an incredibly powerful character such as Jaenelle is, and I can only admire Anne Bishop's artistry in doing so. The techniques are varied - one is that we only see her through the perspective of others, another is that when we first meet her, in the first book, she is a child, and not yet come to her full strength - but, in the end, they achieve the result of creating a character who, for all her power, is still human, real, and vulnerable. In the words of one of the main characters in the first book, "...with her, the Black was not only dark, savage power, it was laughter and mischief and compassion and healing... and snowballs."
Black Jewels has a lot going for it, but there's also a lot you might find it difficult to get past. A good piece of advice to follow is to not leap to too many snap judgments - Bishop's unique characters and world mean that there is at least one main good character, Daemon, who you may initially hate but later come to like, and any number of side characters who may prove to be more important down the road who you should take the time to savor now. But if you like romance, strong characters, an intriguing world, a good plot, and aren't afraid of a little darkness, there's a very good chance these books will become among your favorites.