(FORTUNE Magazine) – Harvey Mackay, chief executive and sole owner of Mackay Envelope Corp. in Minneapolis, has good news for unrepentant self-improvers: You are not finished yet. Sure, you won friends and influenced people, improved your memory, unleashed your hidden potential. But now, trumpets Mackay, 55, in a new book on salesmanship, you can Swim With the Sharks Without Being Eaten Alive. Folks are diving in. Two weeks after the book was published by William Morrow, it reached the New York Times best-seller list. But hey, it couldn't miss. Its flyleaves are spotted with testimonials from Robert Redford, Ted Koppel, 15 CEOs -- several from FORTUNE 500 companies -- university presidents, basketball coaches, a former President of the U.S., and more. Of course, Mackay repays his endorsers in kind, lavishing praise on CEO after celebrity after coach. Don't expect to find anything new here. When pressed the author admits, ''You've probably heard most of what I've said before.'' Expect anecdotes, often more interesting than the sales points they illustrate: While visiting Cuba as part of a business delegation, Mackay learned that Fidel Castro spoke English by luring the Cuban dictator into a discussion of their common passion -- bowling.