This book only has a few things to say, but it says them very clearly, with great case studies, and presents a framework that can actually be followed in practice.
The whole book can be summed up as an explanation of the “usage lifecycle” that details the journey from a user being unaware of your site to becoming a passionate user. There are four hurdles to overcome: awareness (which takes a user from unaware to interested), signup (from interested to first-time user), return visits (from first-time user to regular user) and emotional attachment (from regular to passionate user).
Each of these hurdles presents its own design challenge, and the book shows examples of how popular sites have jumped these hurdles, and provides a way of thinking about each problem and its solution.
There are also details on what it means to have authentic conversations online. Worth a look is this story (linked from one of the footnotes) on How Flickr builds communities online (click on the images at the bottom of the page to advance through the story.
Another insight worth mentioning: the notion of “designing for collective intelligence” – as the user base of social software gets larger, different challenges will be encountered, and need to be solved – the reaction of the community itself becomes part of the design challenge.
Designing for sharing is something that we see regularly, but it goes beyond having a “share this” button on every piece of content. Have you made it as easy as possible for your users to spread the word about content? Can they embed content on their pages?
The final chapter presents the helpful tool of funnel analysis. List out the different steps of your online process, and see where you are losing people. For everyone who gets to your first page, how many make it through signup and actually perform the first task you want them to perform?
Lots of helpful content here. Well worth a read.