I'd like to share my specific motivation for writing Can the Chain Still Hold You?
I agree with Yvain that akrasia is probably a major reason that rationality alone doesn't create superheroes. You might be much better than average at making good decisions based on an accurate model of reality, but that doesn't mean you can follow through with them.
Many people report that their thinking is clearer and better as a result of Less Wrong. But despite our many, many attempts to hack away at the problem of akrasia (more: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10), I haven't heard of many LWers conquering akrasia.
But I still have hope that this is possible. In 2006, we finally got a decent psychological theory of procrastination, much better than the old decisional-avoidant-arousal theory. On the timescale of progress in psychology, 2006 is basically yesterday. The first book on how to apply this new theory to daily life was published in late 2010. There is no community of people systematically practicing these techniques and reporting their results.
So it seems to me there is a lot of low-hanging fruit to be scooped up in the field of procrastination research. If we try and test enough things, and especially if our tests our theory-guided, we may be able to learn new things and flip a few causal factors such that the chain of akrasia no longer holds us — at least, not as tightly as before.