Book excerpt: Why do people kill those they love? David J. Krajicek, one of America's most renowned true crime storytellers, explores that question is these 50 unforgettable examples of relationship murders, including spouses, intimate partners and other blood relatives. The killers often are motivated by lust and greed, which Krajicek calls the terrible twins of the Seven Deadly Sins. More than 2 million marriages are celebrated each year in America. Some last forever. About half don't. A simple divorce is the solution for most couples when marriage loses its fragrance. But legal niceties like divorce do not seem viable for certain types of people, those who cannot fathom a life of romantic freedom fettered with debt. In these cases, Krajicek writes, "First comes love, then comes marriage. This is followed by sobering reality, quarrels, regrets, resentment, hostility, frigidity, animosity. Soon, one partner is sitting at the computer googling phrases like 'How to commit murder.'"