Revenge for the Bay of Pigs : PROMISES TO KEEP <i> by George Bernau (Warner Books: $19.95; 642 pp.) </i>

George Bernau was 18 years old when John Kennedy was killed, and he never got over it. One hopes this book will help him do so.

“Promises to Keep” took five years to write. In doing so, Bernau, in his first published novel, has clearly researched both his Warren Commission Report and his Church Committee Report--among other things. And one guesses that he has put not only his time but a great deal of himself into this project.

This is a story of conspiracy and corruption, of assassination, of regicide. For a generation of Americans, it is the story of their age.

Another conspiracy story? Yes. Why would Warner Books pay so much money ($750,000) for another one? Simple. It has a device. The device is this: John Kennedy survived. No, not in the ghoulish Elvis/Marilyn-is-alive-today-and-living-in-Buenos Aires sense. John Kennedy survived the assassination attempt, eventually to disclose his own role in the plot that almost killed him.

Also (and this is a crucial part of the device): John Kennedy was the Last American Hero. Else, why write the book?

Reviewers should disclose their biases. Although Bernau denies this book is a roman a clef, I believe his theory of the assassination is right. I think President Kennedy was the victim of a conspiracy. And I’ve particularly thought so since serving as a member of the Church Committee between 1975-76 when, among other things, we discovered CIA efforts to assassinate foreign leaders, efforts euphemistically characterized as “executive action” and code-named “ZR/Rifle.” The prime target, pursued with almost demented insistence for “executive action,” was Fidel Castro. And the principal assets of these anti-Castro plots were three Mafia figures called Sam Giancana, Johnny Rosselli, and Santo Trafficante, now all dead. Giancana died of “lead poisoning” and Rosselli was killed during the ChurchCommittee’s investigation. On the theory of Hart’s fourth law of politics (nothing of consequence happens by accident), then Bernau’s story deserves attention.

Actually, Bernau tells several stories--one conspiratorial, another political, a third pastoral, in descending order of their persuasiveness. The pastoral story, of the Kennedy marriage, is least convincing. It is too sweet, too perfect--even given a bump or two thrown in by an Onassis figure and someone who most resembles Anjelica Huston at age 15. All in all, given what we know of the complexity of both its partners, the Kennedy marriage was probably a lot more interesting than the somewhat cloying portrayal it receives in “Promises to Keep.”

The political story is this. Having survived three bullets--one to the brain--John Trelawney Cassidy (John Kennedy) chooses not to seek re-election. But his heroic stature enables him to negotiate his brother Tim Cassidy (Bob Kennedy) onto the ticket with Ransome Gardner (Lyndon Johnson) in 1964. Vice President Tim Cassidy begins to separate himself from President Gardner’s hawkish Vietnam policy in 1967, then dies in a helicopter ambush during a tour of Southeast Asia. In a historic reversal, John Cassidy, recently re-elected to the Senate from Massachusetts, picks up his dead brother’s torch and challenges Gardner in the 1968 primaries. Gardner withdraws from the race after losing to John Cassidy in the New Hampshire primary. Thereafter, the contest for the 1968 Democratic nomination seesaws between Sen. Cassidy and replacement Vice President Putnam (Humphrey). Read the book to see how it turns out.

The real story is conspiracy, and this is the one Warner Books (and some television syndicate) paid a lot of money for. And this is the one to read. Because, Bernau says, there were two gunmen in Dallas. They were the remnants of a “ZR/Rifle” team authorized, ironically, by Kennedy/Cassidy in 1961. One was Arthur Strode (Oswald) and one a demented Cuban called Antonio Lopata (a character tailor-made to win Edward James Olmos an Emmy). They are hired by a Mafia-Cuban-exile combine to work retribution on John Cassidy for failing to provide air cover at the Bay of Pigs and for calling off the Castro assassination plots before they could succeed.

Aside from John Cassidy, the story’s other hero is an oxymoronically independent FBI agent called Jim Sullivan. (Bernau loves the Irish.) Resisting cover-up pressure even from FBI Director John Summers (J. Edgar Hoover), Sullivan relentlessly unpeels the onion of conspiracy and, in the end, pays the supreme sacrifice for his troubles. As in real life, anyone involved in the conspiracy by circumstance or who seeks the truth by choice gets eliminated, one way or the other.

Leaving aside the not-so-coincidental timing of the publication date, 25 years after the first Kennedy assassination, one believes uncynically that Bernau was compelled to write this book. John Kennedy (with, it must be said, all his faults) was the Last American Hero. For, within the decade following his death, America went from the noble and idealistic Periclean sentiment of public and national service to the seamy, self-serving Snopesian politics of Watergate. We went from fewer than 10,000 “advisers” in Vietnam and a policy described by Kennedy before his death as “. . . it is the Vietnamese’s war and they must win it,” to an American force level of 500,000, and 50,000 dead. We’ve had an embassy held hostage for months, Marines dead in Lebanon, shuttle disasters from shoddy workmanship, invasions of tiny islands, Iran-gate, and the phony-baloney euphoria of “morning in America” financed by Japanese creditors.

History has been different because of John Kennedy’s assassination, regardless of how one comes down on Tolstoy’s agony over the impact of great figures. With a fractional twist of ballistics, Bernau turns it all around. With five years of effort and a monster manuscript, he has, one hopes, loosed this animus from his soul.

Now, how about the rest of us?