If you want a hard science-fiction novel about digital humans you could read Greg Egan's Permutation City, it's a masterpiece.
One should note that he says people shouldn't expect to just sit down and read a book, but should use a pencil and paper to help figure things out. Though that doesn't apply so much to Permutation City, it does to other stuff like Orthogonal and Incandescence. (From what I've heard Schild's Ladder, too).