Blum was born in Queens, New York, and graduated with a degree in English literature from the University of Chicago in 1977.
He began his career as a reporter in 1979 for The Wall Street Journal. He has also worked for Esquire (where he became as associate editor in 1983), been a contributing editor at New York Magazine (1985-1992), and a regular contributor to The New York Times Magazine (1995-2000).
A 1985 New York Magazine cover story by Blum is credited for coining the term Brat Pack for a group of young 1980s actors.
In 1992, he published his first book, Flash In The Pan: The Life and Death of an American Restaurant, which was named a notable nonfiction book of the year by The New York Times Book Review. He published his second book, Tick...Tick...Tick...: The Long Life & Turbulent Times of 60 Minutes, in 2004.
In 2002, he was named an adjunct professor at the Columbia University Graduate School of Journalism.
Blum was editor-in-chief of The Village Voice from September 2006 through March 2007 (one in a string of editors the publication had in a short period of time), and editor-in-chief of the New York Press from September 2007 through June 2008. In the latter half of 2008, he briefly served as editor-in-chief of the short-lived 02138 Magazine. He has also served as editorial director of its owner (and the owner of the New York Press), Manhattan Media.