Written in the slang of a middle-class teenager from S?o Paulo, it is part diary, part blog and even offers how-to tips for readers looking to spice up their sex lives.

In a month, it has sold 30 000 copies and is already in its third edition - in a country where only a fraction of the population reads books. It is also third on Brazil's bestseller list for nonfiction, neck-and-neck with international hits like Freakonomics by Steven D Levitt and Stephen J Dubner.

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