I second some people's claim that "rationality" can be a double-edged sword in the title, even people who might be interested in the book may have negative connotations. It would fit better in the subtitle, something like:
Think Like Reality: The Art of Being Rational
Quantum Computing Since Democritus got me thinking that we may want a more riveting title for The Sequences, 2006-2009 ebook we're preparing for release (like the FtIE ebook). Maybe it could be something like [Really Catchy Title]: The Less Wrong Sequences, 2006-2009.
The reason for "2006–2009" is that Highly Advanced Epistemology 101 for Beginners will be its own ebook, and future Yudkowskian LW sequences (if there are any) won't be included either.
Example options: