The Kindly Ones (Sandman Book IX) - Neil Gaiman
This is the book that made me want to buy the whole series. The art is more stylized and moves away from the realism (and more typical comic book style) that most of the stories have used, and I found it visually more appealing. The story is largely about wrapping up all the loose ends from the first eight books, and most of the characters we've met along the way show up in large or small roles. The overarching story is about the Furies ("The Kindly Ones"), who have come to hound Morpheus and tear apart the Dreaming—but there's a whole lot more along the way. Unfortunately, since I don't have the whole series, I wasn't able to flip back and remember how all the characters are related to one another. It's still a great read.