Since I last wrote about it some 21 months ago, LibraryThing, the bibliocentric social software site, has been chugging past major milestones (its first birthday, its 10 millionth book, passing Harvard to become the second-largest "library" in the United States), and each time it has, I've meant to take that as an opportunity do a follow-up post on the service. But each time, I have dragged my heels about actually writing anything, and the moment has passed. Well last week, LT celebrated its second birthday, and I have pledged to myself to mark this anniversary whatever the cost.

At over a quarter-million members and 18 million catalog entries, I think it is fair to say that LT has been pretty successful. They've gotten some good press, they've internationalized into 23 other languages, and they've even hired a few more employees. What's interesting to me, though, is how badly, for all my enthusiasm about the site, I misunderstood and underestimated what LibraryThing was all about.

When I first signed up for it, I thought of LT as del.icio.us for books, and I wondered publicly whether such a concept could really work given the inherent differences in cataloging books vs. cataloging websites. By fixating on LibraryThing as a catalog, I was ignoring the other important part of the site: its social component. Nowadays, "social networking" and "social software" have become such buzzwords that it is hard to find a website that does not trumpet some "social" feature or another. LT, however, has really put some substance behind the buzz and developed in some interesting directions.

A striking example of LibraryThing's approach is how it addressed the question I'd fretted so much about when I last wrote about the site: namely, how to deal with the proliferation of editions, translations, etc. that complicate our idea of what constitutes a "book." A couple months after I posted those concerns, Tim Spalding unveiled LT's "works" feature, which let members decide which books belonged together for the purpose of aggregating ratings, comments, owners, etc. It was an elegant solution to a thorny problem (which LT has gone on to apply to authors and tags as well) that hinges on the social nature of books:

The purpose of works is social. Books that a library catalog considers distinct can nevertheless be a single LibraryThing "work." A work brings together all different copies of a book, regardless of edition, title variation, or language. This works system will provide improved shared cataloging, recommendations and more. For example, if you wanted to discuss M. I. Findley's The Ancient Economy, you wouldn't really care whether someone else had the US or the British edition, the first edition or the second.

There's an interesting symmetry here: books are connected if they can, in turn, be used to connect people. This basic idea of connecting people through books informs almost everything LibraryThing has been doing these last two years: group pages, partnerships with swap sites, library recommendations, "connections", and others. This stands in contrast to a site like del.icio.us, where the social component, though by no means unimportant (see my previous effusions on del.icio.us's second birthday), is much more impersonal. Yes, you can subscribe to another person's links or recommend links to another user, but you really aren't going to forge a relationship with that person through del.icio.us.

I don't want to privilege one approach over the other. I love both del.icio.us and LibraryThing, and I am not sure either would work nearly as well as it does if it adopted the other's methods. The point I am tryong to make, I guess, is that LT has done a good job of building its own coherent and, I would say, compelling identity and, in the process, expanded my ideas of what a "social" website can be. So, happy birthday, LT, and many happy returns.