I read at the thread that some people is using wikis for documentation. A wiki is great to discuss ideas and post short content, but not enough if you write a book. You’ll need to quickly jump from chapter to chapter, move content, and that is tricky even with confluence. It’s painful to cut and paste between big chunks of text written in wiki syntax.
Im a happy confluence user, but I prefer docbook for documentation with more than a few pages.
Carlos Sanchez's Weblog 
I read at the thread that some people is using wikis for documentation. A wiki is great to discuss ideas and post short content, but not enough if you write a book. You’ll need to quickly jump from chapter to chapter, move content, and that is tricky even with confluence. It’s painful to cut and paste between big chunks of text written in wiki syntax.
Im a happy confluence user, but I prefer docbook for documentation with more than a few pages.