Books are content types that any user with an account can edit. They are organized hierarchically, so that each book page represent a chapter of the larger book. Another advantages of books is that they have a printer friendly view for easy printing. The printer friendly view includes all child pages of the book page you want to print. They are the closest thing to a Wiki on LondonCommons.net.
Unlike a Wiki, there is no Wiki markup for adding links to a document. Links are done the same way as everywhere else on the website using the TinyMCE editor. Similar to a Wiki, book pages have a revision history. To see past revisions of a book page (and most of the other content types too) click on the revisions tab above the title of page.
Comments do not show up in the printer friendly view. This means that the comments area of each book page can be used by its authors to discuss the document. Editorial decisions, brainstorming, and even disagreements can be kept out of document itself by keeping them in the comments.
Book pages by their nature are very flexible. They can be used for collaborative creative writing, because there are no limits on size and any users is allowed to edit. They can just as easily be used to create a user contributed directory. Each child book page could be a category or letter from the directory.