Selwyn Raab, an investigative reporter for The New York Times and other news organizations who, in exacting detail, explored the Mafia’s many tentacles, died on March 4 in Manhattan. He was 90.

As a boy on Manhattan’s Lower East Side, Mr. Raab saw the mob up close. There, he told Time magazine in 1974, he was “surrounded by the kind of legendary criminals you read about — bookmakers, con artists, Jewish and Italian gangsters.”

“I grew up with guys I later covered,” he said.

The mob had his enduring attention, and it led to his definitive 765-page book on New York wiseguys, Five Families: The Rose, Decline, and Resurgence of America’s Most Powerful Mafia Empires, published in 2005.

Mr. Raab received many honors for his work, including the Heywood Broun Award from the New York Newspaper Guild, and an Emmy for his work on “The 51st State,” a WNET program that dealt with New York City issues. He joined The Times in 1974 and worked there for 26 years.