The New York Times has a slideshow of the "Comings and Goings at Mark Twain's Last Home, as Told by the Guest Book." We can read Twain's own comments on the guests! Such as this one about a girl called Margaret who came for a visit on April 10, "It is an event: an event like the advent of spring after winter." There is also an accompanying article with a "hip" comparison to the 21st century phenomenon of "tweeting."
In a webpage called Memories of Mark Twain in Bermuda, you can see pictures of, and read about, Twain and Margaret.
You can find Twain's fictional work on our shelves under F TWA, or his nonfiction in the 818 section. Twain himself is covered in the biography sections--adult, B TWA, and children's J B TWA.