Glow / Tim Jordan.

Enhanced descriptions from Syndetics:

A man battles his addiction to a devastating nanotech drug that steals identities and threatens the survival and succession of mankind as a galactic species.

After the Nova-Insanity shattered Earth's civilization, the Genes and Fullerenes Corporation promised to bring humanity back from the brink. Many years later, various factions have formed, challenging their savior and vying for a share of power and control.

Glow follows the lives of three very different beings, all wrestling mental instability in various forms; Rex - a confused junkie battling multiple voices in his head; Ellayna - the founder of the GFC living on an orbital satellite stationand struggling with paranoia; and Jett - a virtually unstoppable robotic assassin, questioning his purpose of creation.

All of them are inextricably linked through the capricious and volatile Glow; an all controlling nano-tech drug that has the ability to live on through multiple hosts, cutting and pasting memories and personas in each new victim.

In this tech-crazed world where nothing seems impossible, many questions are posed- what makes us who we are? What is our ultimate purpose and place in this world? And, most frightening of all, what are we capable of doing to survive?

File Under- Science Fiction Hivemind | One More Fix | No Escape | Run Like Hell