The All Souls Trilogy includes A Discovery of Witches, Shadow of Night, and The Book of Life. The protagonist is Diana Bishop, fictitious descendant of factual Bridget Bishop, who was executed during the Salem Witch Trials. Diana is a present-day historian, and the books follow her as she comes to terms with being a witch and solves the mystery of an old manuscript. The author's interpretation of supernatural lore is very interesting, as she brings a scientific approach to it. The books also take an interesting path into historical fiction and introduces some great characters along the way.
Each of the books is quite long, but I ended the trilogy wishing there was more. I definitely recommend these books. There's much more I could say about the story, but I won't to avoid spoilers. If you've read it, leave a comment, I would love to know your thoughts.