NB: The following opinion is seveal years old by now. Not sure it is still valid but revisiting the book is not a priority right now either. YMMV.
After Life by “Simon Funk” (an alias). Highly intelligent, self-published (but freely available online ) writing by an A.I. researcher. Starts with mind-uploading and moves from there. Got a lot of praise in a lot of futurist blogs when it first made the rounds a few years back. I actually bought a hard-copy somewhere and I am glad I did.