Ask HN: Sales book recommendation?

I've been working as a freelancer web/software developer for almost a year now; however, I feel that my sales cycles are long-stretched at best. I have no intention whatsoever to "blame the economy" (as it seems to be fashionable nowdays); I'll take full responsibility for this, and thus turn to the entreprenour culture blooming around here:

What books, blogs, or fundamental understanding has made the biggest impact on your sales, and bottom line?

(No cliches, please.)