Writing books and writing software have a lot in common. One can write code or books in different languages and styles, let the story go different paths, a review is recommended before publishing, ...
I dont know if unit testing for books exist - but also a story in a novel has to follow some rules. For instance it would not make sense if the murder is the same victim or the detective in a crime story.
So if software can be assembled and built using a continuos integration server why not do the same for books and documentation.
The Pharo community addresses this as well:
from today on all pharo books are now built in one place at the Pharo CI server.
Soon we will also have a http://books.pharo.org page.
If you can wait for more have a look at: http://pharo.pharocloud.com/pharobooks