This novel is like a Buddhist riddle designed to undo the damage of emotional aversion to encourage a kind of enlightenment in the reader. This can be seen in the passages about the Holy Mountains in Asia. These are the location of the Buddhists and their historical mistreatment by communists. In this story, there is a mischievous spirit who entangles himself in the stories of the family. This raises the important question of the title: What exactly is Ghostwritten?
One answer to this titular idea is that the entire plot of the story is contrived by the author. Because of the suffering of the characters, what the reader can see from this puzzle of a novel is that the characters suffer because they are being conspired against by an author. The idea of the soul as a spirit gives the characters a "haunted" quality, because the author himself designed the spirits of each character to work in their own way.
In other words, there are terrorists because the author wanted to include stories about terrorism. There are mystics in Holy Mountains because the author willed it into reality. There are ghosts behind the system that make the plot weave in and out of itself, for beauty's sake. Eventually, the reader can see that these ideas of divine conspiracy are an argument about reality itself. The Buddhist riddle has its solution in the narrative structure of the human experience.