Greg Egan gets quite deep into virtual reality and subjects such as artificial life, uploaded conciousness, etc. I'd recommend the novels
Zendegi and especially
Permutation City. There are also some short stories available free online from the
author's website, e.g
Wang's Carpets.
Edit: One I didn't enjoy as much (but others might) and has interesting ideas around augmented reality is
Vernor Vinge's
Rainbows End.