The Mariana de la Mar series of medieval novels. WARNING: These books all contain sexually explicit scenes unsuitable for young readers. And certain readers of other ages may find the scenes depicting medieval witchcraft, torture and prostitution, not to mention the medieval Undead, all a little too much.
This fantastic drawing by Vania Zouravliov conveys perfectly the atmosphere I have tried to create in my third Mariana novel, The Undeparted Dead. (And this, I have to say, is exactly how I see Mariana herself!)
You can find more of his stunning drawings here, for example, and here.