Google Book Search shows a map that contains some of the locations referenced in a certain book (like War and Peace). If you click on a red balloon, you'll see an excerpt from the book and other pages that talk about that location. The mashup can be found in a special page that shows more information about a book, including a summary, related books and links to book stores. Inside Google Book Search shows more examples of books that have "a good number of quality locations".
Another interesting site that brings maps and books together is Gutenkarte, "a geographic text browser, intended to help readers explore the spatial component of classic works of literature", but its interface is more difficult to use.