No sooner had David Talbot resigned as editor of than he was shopping around a book proposal. And he got a quick score. Such was the lure of subject and author that his Brothers, a new look at the closing years of Robert F. Kennedy's life, was immediately snapped up for the Free Press by editor Martin Beiser. He got world rights from Sloan Harris at ICM. Talbot's book will be based not only on interviews with Kennedy family intimates but also on access to some of RFK's personal papers. He will show that the Kennedys felt utterly estranged from such institutions as the Pentagon, the CIA and the FBI, and that one of the motives behind Bobby's run for the presidency was to unearth the secrets of his brother's assassination.