Kirshbaum said that he will likely pursue a career as a literary agent, so he "can work with authors in a more intimate way without all the stresses and strains of administering a large company."
"After 30 years of passionate involvement with our wonderful book company, I have decided that it is time to turn the reins over to a team that can provide the energy and leadership which our vibrant enterprise demands," the 61-year-old Kirshbaum said in a company e-mail.
"When I arrived as a marketing executive at Warner Paperback Library in 1974, we were doing about $5 million in business. This year we will surpass $500 million in sales."
In a separate e-mail sent Monday, Time Inc. executive vice president and CFO Richard Atkinson said the resignation was "entirely Larry's decision."
"His business has had a great run of best sellers, is going to post all time record financials this year and is blessed with an experienced and talented management team that can take the Time Warner Book Group to new heights," Atkinson said.
"So, Larry has chosen the perfect moment to slow down, move onto something less stressful and take the time, as he puts it, to smell the roses."
Kirshbaum is known for his raspy voice, candid talk and abiding affection for his alma mater, the University of Michigan — he told The Associated Press on Monday that he can be found rooting for the football team on Saturdays at a local bar with "300 other screaming fans." Between games, Kirshbaum managed to publish such best sellers as Malcolm Gladwell's "Blink" (search), Jon Stewart's "America (The Book)" (search) and James Patterson's "4th of July" (search).
He will stay on until the end of the year, when he will be succeeded by David Young, currently chairman and CEO of the Time Warner Book Group UK.
Kirshbaum graduated from Michigan in 1966, worked as a correspondent for Newsweek and co-authored a book about student protest, "Is the Library Burning?" He joined the marketing department of Random House in the early 1970s, then moved to Warner Books in 1974. He was named president of Warner Books in 1984 and promoted to chairman of the Time Warner Book Group, which includes Warner Books and Little, Brown and Company, in 1996.