I'm looking for a novel, the main character is a smart man (doctor or physicist) who just die, his spirit have been harvested by a superiors consciousness. The man ask to the superiors consciousness to let him "die" (let his spirit disappear), what is denied. The man then promise to try everything possible to disappear or kill the superiors consciousness. It respond by "That exactly what I want from you". Indeed the superiors consciousness want to die too and try to find a way to disappear by collecting smart minds in the hope one of them find the solution.

It may be one of these.