A self-confessed modern romantic, "a man without traditions,'' George Gershwin wrote hundreds of lively, expressive, perfectly crafted songs, the opera Porgy and Bess and longer, more pretentious works that, 50 years after his death, remain in the repetory. Arguably, he is the most popular American composer of all time. In describing Gershwin's life and career, this long book, by a prolific writer on American music and military aviation, lists the highlights, repeats many familiar anecdotes and, curiously, does not include in the bibliography the Charles Schwartz biography that for some 15 years has been regarded as the standard work. For many readers, the most interesting part of this book will be the epilogue describing the later career of Ira Gershwin, who died in 1983, after ``he had just enjoyed some of his favorite chocolates.'' Photos not seen by PW. (September 18) - Publishers Weekly.