After threat of a libel suit, the publisher HarperCollins is taking the rare step of destroying its inventory of a new book that attacks James J. Cramer, the journalist and former hedge fund manager. James A. Fox, vice president and general counsel of HarperCollins, conceded in a letter to Mr. Cramer's lawyer that three pages of the book, "Trading With the Enemy," by Nicholas W. Maier, contained false assertions that Mr. Cramer had traded on inside information about the Western Digital Corporation. Lisa Herling, a spokeswoman for HarperCollins, said the company would pulp the roughly 4,000 copies of "Trading With...