GRUMBLES FROM THE GRAVE by Robert A. Heinlein, edited by Virginia Heinlein (Del Rey: $5.95). Although the late Robert Heinlein intended "Grumbles" as a legacy for his widow, the image of the writer that emerges from this collection of letters is decidedly unflattering. There are flashes of interest in the early correspondence, when Heinlein was struggling to establish himself in the pulp science-fiction magazines and in juvenile fiction. But he generally comes across as a censorious arch-conservative, furiously railing at anything that incurs his disapproval, from gun control to Freudian psychoanalysis. He describes the public opposition to nuclear testing as "this pacifist-internationalist-cum-clandestine Communist drive to have us treat atomics and disarmament in exactly the fashion the Kremlin has tried to get us to do for the past twelve years." It's also painfully obvious that Heinlein was a writer whose ego exceeded his talent. Despite the cult status of "Stranger in a Strange Land," his best works remain the boys' books he wrote during the late '40s and early '50s ("Time for the Stars," "Tunnel in the Sky," "Starman Jones," etc.)--but he fails to perceive the gap that separates his work from "Ulysses" or "The Catcher in the Rye." "Grumbles" can only tarnish Heinlein's reputation.