Cohen was not among them, alas. He seems to have given only three for-the-record interviews, ever, to reporters. But his silence may also have been liberating to Kolhatkar, who was not psychologically constrained by gratitude to her subject for letting her in. She does not spare us her judgments of Cohen or of SAC Capital or of the hedge fund industry. They are not favorable.

For those who do not remember: SAC Capital was once one of the most powerful hedge funds on Wall Street. Cohen, its fabled steward, was different from the other colossi of the industry (George Soros, Paul Tudor Jones) in that he never seemed to have a grand unified field theory of investing. Rather, he had a talent for reading the market’s movements and a freakishly high threshold for tolerating risk.

And, miraculously, he was on the right side of almost every transaction — “something that seemed, at least on the surface, to be impossible,” Kolhatkar writes. This improbable winning streak eventually got the F.B.I.’s attention, when it was investigating insider trading at a different hedge fund, the Galleon Group, and managed to lock up its chief.

But Cohen never faced a criminal charge. The most the government could do was order SAC Capital to shut down in 2013 and fine it $1.8 billion — a figure that sounds like an awful lot until you learn that Cohen had almost $10 billion of his own money left over, which he could still trade and invest as a private family office.

Image Sheelah Kolhatkar Credit... Bloomberg Business Week

Kolhatkar never reduces anyone in “Black Edge” to a stone-gargoyle grotesque. But Cohen certainly goes across the street and around the corner to reify certain stereotypes about hedge fund managers. Monster estate in Greenwich, Conn.? Check. (The backyard has a 6,000-square-foot ice-skating rink, plus a shed for the Zamboni.) Priceless art collection? That, too. (It includes Damien Hirst’s shark suspended in formaldehyde, a metaphor so literal you don’t know whether to laugh or cry.) Nasty divorce? Oh, yes. (You know things are ugly when your ex files a Freedom of Information Act request to get the goods on you.)