My opinion is that the main conflict in the novel is really figuring out how much of the escape artist everyone must be in order to survive in our every day world.  If you aren't willing to test the limits a little bit and try to see beyond your everyday circumstances, you are in many ways a victim of them.  Because Joe and Sammy both find ways to escape their reality in different ways, the book explores how much they can and can't escape and when they have to be present to confront the stark realities of life and when it is healthy and helpful to escape them in whatever mode you choose.