LIBRA <i> by Don DeLillo (Penguin: $4.95) </i>

This fictionalized account of the assassination of John F. Kennedy offers the literary equivalent of a docudrama. Don DeLillo’s version of the popular conspiracy theory seems to have been modeled on the Iran-Contra affair: The President’s murder is the work of a band of zealots who believe that the business of governing is too vital to be entrusted to the government.

A cabal of renegade intelligence agents, mobsters and Cuban expatriates stages an assassination attempt whose failure is intended to provoke Kennedy into deposing Castro. Their plot backfires when Lee Harvey Oswald, a disaffected pawn in the hands of smarter, deadlier men, proves to be a better shot than they anticipated.

Grim, gritty and depressing, “Libra� lacks the off-the-wall humor of DeLillo’s other novels. The revelations of the Iran-Contra hearings and Oliver North’s trial may have made the story seem entirely too probable; or the death of President Kennedy may still be too emotionally charged a subject to allow the reader to enjoy an account of its willful creation.