This reminds me of the very riveting book "Metamorphosis of prime intellect", in which,

- Spoiler warning -

an AI is programmed to obey Asimov's three laws. But due to a yet unknown quantum effect (this part is a bit far fetched) it basically gains god-like powers and virtually instantly distributes itself over the galaxy and eventually replaces the world with a virtual reality. That book was quite a ride. It's available for free: http://localroger.com/prime-intellect/mopiidx.html