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"Inside Facebook", a look at Facebook from the perspective of a former engineer, is out in paperback on Amazon this week - it was originally released in the Fall of 2006.
Author Karel Baloun, who occasionally writes here at Mashable, is offering Mashable readers free access to the ebook version for 36 hours - you can read it at http://www.fbbook.com/mashable. We'll try to get you a weekend extension, too. ;)
Spanish and Chinese editions of the book are expected at the end of this month, with the Chinese version being translated by Yeeyan, the social translations site. Baloun is currently working at mEgo, a really cool way to manage social networking profiles. (He's also working on Ptrades, which I'm not so hot on.)