Watch out Amazon (well not really) here is Reader2, from the maker of MyProgs (the interface and functions are basically identical), this time round this folksonomy is dedicated to books.

From the website:

"This site allows you to keep a social list of the books you read and/or recommend. After you sign up you can add books to your unique list. You can view anyone else's books and they can view yours. Extra user-defined data can be added to each book entry to organize and describe the book further such as descriptions, links, and tags. You can use tags to categorize (and thus organize) books so that you and others using this site will have an easier time finding new and interesting books to read."

Front page

• List of Latest Tags

• Link to a Tag Cloud
• Link to Popular Tags
  

Each entry has:

• Date of entry
  
• Title of Book
  
• Author of book - clicking on this will show all books by this author from within a users account
  
• User - clicking on this will show the users account
  
• Description - with a link to go to the native site
  
• Status Tags (a choice of) - now reading, recommended, favourite, to read (within a particular users account, not all accounts)
  
• Type Tags (a choice of) - Fiction, Educational, Technical, Documentary, Scientific, Children's, Religious
  NOTE: this is a field when you add a page, but when you view a bookmark it lacks a Type Tag (so what's the purpose-maybe it hasn't been imnplemented yet)
  
• Normal Tags - make up your own (if a bookmark has more than 2 tags there is also a "++" symbol, clicking on this will show all bookmarks from all users with these tags intersecting...I suppose a boolean AND search)
  
• ? Users - links to a URL page of a bookmark, showing all instances of users who bookmarked this URL (and a list of the common tags)
  
  Images of book covers would be a good addition

So as you can see besides the user-defined tags, there are some other inbuilt tag to choose from, allowing for more structure and context...so there is still the user defined part, but also some centralised organising (this still requires the user input)...kind of have a choice of browsing user-defined tags or tags users choose from a centralised list.

Tag page

Similar to the front page, but the list on the left is "related tags"


User page

Similar to the front page, but clicking on tags will be within the user account, also clicking on an author will be all bookmarks with that author within the users account,


Search

Great thing about searching is that as soon as you enter 3 letters it starts offering suggesting

Search your books

Search your tags

Search books from all users

Search tags from all users

Combine search to include or exclude tags

...and you can also limit your search to popular bookmarks

I couldn't get the book search to work within just my account or all accounts...I searched for words in the title, words in the description, but it wasn't finding anything (probably still in the early stages of development)

Thr to-do list mentions exporting features, ratings, tag bundles, and more RSS feeds

RSS feeds

Sitting there waiting in the top right hand corner of each page...there is even feeds for the author field, and the status field

...only one lacking is for the URL page of each bookmark (ie. ? users bookmarked this page)