Tattletale Kevin Federline is ripping the lid off his stormy marriage to Britney Spears in a bombshell memoir titled You Thought You Knew , and RadarOnline.com can reveal the fragile pop princess is panic-stricken and vowing to strike back in revenge if her ex publicly humiliates her.

The 47-year-old DJ and former backup dancer's book launches on October 21 and is being plugged as a memoir of "fame, fatherhood and the private cost of public life – from one of pop culture's most misunderstood figures." Article continues below advertisement

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Federline, who's had custody of the former couple's two sons, Sean Preston , 19, and Jayden Spears , 18, since 2008, when Britney flipped

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