If you're interested in a time travel story carried to its convoluted extreme, you might consider Dinosaur Beach, by Keith Laumer. It's currently available from Baen as part of Odyssey.
http://www.baenebooks.com/p-301-odyssey.aspx
Otherwise, my favorite time travel story, Time and Again by Jack Finney, appears not to be available as an ebook. Although it looks like it might be out as an audiobook.