A funny thing happened on the way to Jonathan Karp’s musical debut: He became one of New York’s top book editors. Karp, responsible for best sellers like The Orchid Thief and Seabiscuit at Random House, has written a musical comedy, How to Save the World and Find True Love in 90 Minutes, set in the bookshop of the United Nations. Now head of the Warner Twelve imprint, Karp says, “I moved to New York in 1989 intending to do theater, but I got so fascinated by publishing that it’s taken me all this time to do it. I’ve been writing this for seven years. It’s 90 minutes, so I guess that comes to about 13 minutes per year.” He’s gained new sympathy for writers. “There’ve been many times when I’ve written ‘make it funnier’ in the margins. And man, that’s a tough note to get. If I could have made this musical funnier, I would have, believe me.” The show opens November 12.