I am looking about a story, where dreams where commercialized. The protagonist is a professional dreamer, who basically chooses what he dreams and sells the dream, like a TV show. The antagonist works for the same company, but is a more talented (master or grand master?) and is capable of dreaming virtual worlds, where people can actively partake in the fantasy instead of just consuming it.
The antagonist then goes crazy. I think the cause was a combination of his mother dying (weird relationship there) and his girlfriend leaving him. This causes many people to become trapped in his dream and the protagonist has to enter the dream and end it from within.
I think it is from the Vance/Zelazny/Farmer period and the book was not too thick. Any ideas?
Some more details came to me while thinking about it: the ex-girlfried of the antagonist is one of the persons trapped in the dream and I think she ends up with the protagonist.
Also at some point in the past, the antagonist helped the protagonist make his dreams feel more real, by giving him relevant source material (books, movie?).