Beyond Goodreads: book-based social networking

It's been awhile since I last posted about my travails as an independent author, and one of the trickiest and most time consuming activities for any author is marketing. That's why I decided to write a short blurb on a few of the book related social networks I've come across since my books were published last year.

Currently, I know of three: Goodreads, Shelfari, and LibraryThing.

So here's what I think.

Goodreads 
What I like: free, easy to use, vibrant community of active members, meeting other authors, Read to Review programs, groups, message boards, free blog, author dashboard, html tips, ability to edit reviews and blogs you've written, ability to post reading status updates, talks to Facebook, ability to follow reviews, become a fan, block people from following you, friending

Am I addicted to it: yes

What I don't like: can't save a review in progress, have to finish in one sitting, book setup as an author is a pain in the behind (worth it, but painful), you have to upload your own picture of your cover or your book has the dreary generic look

Shelfari 
What I like: the realistic looking bookshelf, the review interface, the ability to add book details like characters, locations, etc in a wiki format (and not be a librarian), it's free, ability to import books from your amazon.com purchase history (and pick which ones to exclude/include), contribution ranking (fun), public messaging (though this could be a downside too), groups and message boards, ability to follow/friend others and block others from following you.

Am I addicted to it: no, but there's potential

What I don't like: no blog except the shelfari site blog (can't write your own), shelfari blog is on another webpage with no links back to main site, left/right arrows on the shelves instead of finger swipe option (only an issue because I use a tablet), other than groups and book review/info interfaces there's no way to share status updates, no way to add more shelves or customize them

LibraryThing 
What I like: friend finder, ability to add website links in your profile (awesome to link to author profiles on amazon, goodreads, smashwords, etc.), recommendations when you add a book (based on the book you add), permalinks to individual reviews from the book's reviews feed, "conversations" which are links to boards discussing a particular book (awesome for authors who want to see what people are saying without following everyone), concise book stats including members who added it, popularity, reviews, average rating and mentions (each of these, except rating, links to a list so you can see what feeds into the stat), links to buy and swap from a book's page (includes audio), ability to create an author profile, site "talk" and groups

Am I addicted to it: no, but there's potential

What I don't like: have to pay to add more than 200 books, zeitgeist is weird and I don't know what it's for, Import from Goodreads (what is it supposed to do?), have to pick a short screen name (couldn't use my full name), some of the links are a little buggy on my tablet, plain interface is kind of blah

Are there more out there? Probably, I just haven't found or tried them out yet.

Let me know which sites you like and share your opinions of these three. I'd love to hear what you think!