It would be a good idea but many of the stories people write there are more so stories of a character's history, their personal story, many of them just to be shared oocly. There's nothing stopping them from putting their auto-biographies up for sale but I'm not sure how many would.
The main idea though about having a market for books would be good. It would just be hard to start as it would most likely have to be created by players who don't take much value in books. To have a successful book economy I think two things would be needed:
1. Players writing books about things other than themselves (actual books of knowledge)
2. Knowledge having a greater worth in Planeshift.
As of now most things that are in books come in handy for a few quests and for helping roleplay by providing details. If knowledge ever becomes worth more than that then we value it now then a real market for books could begin