The Neuro, Book 1: The Crystal Sphere by A. Livadny

Alex is one of us. An office rat during daytime, he spends sleepless nights playing his favorite MMO game: a familiar, predictable world which is about to collapse. A new virtual universe arrives to replace it, aggressively devouring all others: the Crystal Sphere.

Alex gets involved in testing new technologies which promise to revolutionize gaming. Fitted out with a neuroimplant which provides a 100% authenticity of experience, he has to survive in the Crystal Sphere against all odds. What is he turning into? Will he become yet another expendable test subject - or the first player to transcend reality?