Dan Simmons, THE FIFTH HEART

I found the premise hilarious: Henry James, depressed over his sagging book sales, goes to the banks of the Seine, where he plans to throw himself in. (OK, maybe that doesn't sound funny, but wait.) There, he meets Sherlock Holmes, who is depressed because he is beginning to figure out that he's only a character instead of a real person. Add a murder mystery. Add cameos by just about everyone from the late 1800s (Wilkie Collins, Henry Cabot Lodge, John Hay, George McClellan, Mr. Lincoln, etc.), and the World's Fair in Chicago. Twist what you think you know about Professor Moriarty and Irene Adler and Dr. Watson and Sir Arthur Conan Doyle. Add in the sort of cleverness you find in Shakespeare in Love. (Here's an example: "The turn of the social screw at the dinner party [Henry James] had attended including inviting five couples . . . who were comprised of four of the women having illicit affairs with no fewer than five of the men present.") I wouldn't say this book is a quick and easy read--it's dense and you have to be paying attention--but I totally enjoyed it.