Please move this to the main page. I'd love to see it done; I don't know if there's anything I could contribute in the way of time and knowledge.
I also second (third?) the suggestion for trying to make it a companion to The Art of Rationality. Desrtopa, why do you think fewer people would buy it if they came together? Is it because books with workbooks attached look intimidating?
I liked the idea of a separate, electronic format for several reasons:
Note: This was originally posted in the discussion area, but motions to move it to the top level were made.
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My own desire to improve my rationality coupled with some posts criticizing LessWrong not too long ago led to an idea. For reference, the posts I mean are these: