Not a book, a graphic novel--Alan Moore's From Hell.
Heard a lot about this one and I agree, there's a lot more going on here than what actually found its way into that awful movie adaptation.
It's a perfect marriage of text and art, I think. The problem with Moore is that, in something like Watchmen, I never really thought the artwork measured up; the impression I got was that as long as the artist could draw all the details Moore wanted to put in, or draw the equivalent of a close up, or a zoom in, or a match cut, then Moore was happy.
With Eddie Campbell, I think he's met his match. Campbell's drawings evoke Victorian England in a way that helps Moore's text--enhances the period feeling (they look like ink sketches--storyboards for some Victorian idea of an animated feature), possess a beauty all their own, and still get in all the details and camera moves Moore wants.
And it's not a literal visualization of the source book, Knight's The Final Solution: there's an appreciation here of the geographical and architectural features of London that immerses you in a web of dark, unseen forces long before Jack starts cutting up his first victim--a web so pervasive when Netley starts vomiting, you don't raise an eyebrow in puzzlement, you nod your head in sympathy. There's a gift for characterization--Moore's finest talent, I think--that I can't imagine Knight could ever match, much less surpass.
His sketches of Marie Kelly and Abbeline are very fine, especially the touchingly awkward pas de deux the two perform in a pub, the resolution of which is particularly knotty--she may have lied to him, but reason one makes her look like a bitch (and adds all kinds of shadings to that burst of anger Abbeline vents, early in the novel), reason two makes of her a particularly tragic figure forever beyond his grasp. Even William Gull earns our sympathy, and Moore's take on his final act of murder and the reason why it went the way it did is perversely moving (I only wish you could glean it from the actual pages and not from the appendix, as I did--well, I suppose it's possible, but that's how it happened with me).
Finally, there's a mystical vision towards the end of the book that ties everything together, causes us to feel interconnected in a more profound way than Gull's citywide pentagram could ever hope to achieve (can't help but suspect, though, that Moore borrowed this 'vision' device from Stapledon's Starmaker).