"He's Just Not That Into You" is a self-help book written by Greg Behrendt and Liz Tuccillo, published in 2004. It aims to help women understand the signs of romantic interest and disinterest in men. The book emphasizes that if a man is not making an effort to pursue a relationship, it is likely because he is not genuinely interested. The book is based on a popular episode of the television series Sex and the City and has been adapted into a film in 2009. It provides straightforward advice and anecdotes, encouraging readers to recognize their worth and avoid wasting time on unreciprocated feelings.