I made it about half way through Steven King's Cell novel and I ended up losing my copy and never finishing it. I understand that the film will be released this year. Does the book ever reveal the source of the signal? It's been on my mind recently. Appologies for any spoilers. Thank you.
I do not have the book handy, though I will try to get more details later. However, it is revealed that
The cell signal is the work of terrorists. We also find out that they just wanted to destabilize the world a bit, not turn it into an actual dystopia. Something went wrong, though I do not recall what, exactly.