The Gang’s All Here : THE FALL OF THE GODFATHER: The FBI and Paul Castellano <i> By Joseph F. O’Brien and Andris Kurins</i> ; <i> (Simon & Schuster: $22.95; 364 pp.) </i>

Until recently, the literature of the mob has been a dreary collection: one book after another filled with the dry, police-style retelling of crimes, an almost biblical obsession with the lineage of crime families, or killers’ confessions with no perspective. Nick Pileggi’s “Wiseguy” was a breakthrough: In a strong narrative, we got to know, maybe a little too well, some real Mafiosi. His thugs were completely demythologized and deromanticized, but still fascinating.

“Boss of Bosses” is another kind of breakthrough. Authors and FBI agents Andris Kurins and Joseph F. O’Brien come to an understanding of the fearful symmetry between the codes of honor of the good guys and bad guys in the ongoing war between the mob and the government. And they mete out respect and contempt for soldiers on both sides who break those codes.

The book also is a breakthrough because FBI agents still in the bureau show us not only a number of morally complicated Mafiosi but also the complexity of their reaction to these dark, violent and sometimes perversely honorable men. In fact, Kurins and O’Brien may have broken through too far. The FBI fired them for allegedly breaking bureau rules in doing their book.

The Boss of Bosses is Paul Castellano, the former head of the Gambino crime family of New York, the largest and most successful Mafia family in America. In a classic mob hit, Castellano and his bodyguard were shot down in the street in front of Spark’s Steak house in Manhattan in December of 1985. (It is said that when the news broke on the night of the shooting, a New York radio personality, while on the air, called the restaurant and asked for a reservation in the “nonshooting section.”)

The death still looms large in Manhattan. John Gotti, the current boss of bosses, came to power over the dead body of Castellano. This year, Gotti probably will go on trial for the murder.

This is an intimate book about Big Paul. It is the story of a former Godfather suffering from diabetes-induced impotence who had a penile implant so he could better communicate with his Columbian maid Gloria. It is about the capo di tutti capi who managed a violent multimllion-dollar crime machine but couldn’t persuade his wife to take his dirty trousers to the cleaners. It is the tale of the Lear-like unraveling of Castellano’s public criminal authority and the private disintegration of his long marriage to Nina (a no-no for upper Mafia management).

We are privy to these intimacies because for four months in 1983 our two FBI agents bugged Castellano’s kitchen. It was the deepest known penetration at the highest level of mob business--the business of cement, murder, meat and pornography. Some of the information gleaned from the tapes became part of the famous “Commission Case” in which the leadership of five crime families were convicted of conspiracy in New York. Castellano was killed before that trial. Information from these tapes has been used in eight other mob trials.

But the bug cut two ways. Castellano became a human to the agents, one they liked in many ways. Their feelings about him became so complicated that Agent O’Brien actually refused to participate in one case the FBI was building against Castellano because he thought it was a frame-up. Ironically, when O’Brien and Kurins planted the bug, they also planted the seed of Castellano’s destruction, by showing he was vulnerable.

The bug captured 600 hours of some of the most boring and breathtaking conversations you’ll ever overhear and some of the funniest. Listen as the Godfather and his pals discuss their friend’s health. “Cousin of mine moved to Arizona for the climate,” said Funzie Mosca. “How’d he like it?” asked the Godfather. “He died. Caught cancer.” “You don’t catch cancer.” “He did. His girlfriend had it.” “She die too?” “No. Strange, isn’t it? ‘Scuze me, I gotta go outside and spit.”

The book is a hilarious, rambling and sometimes pathetic story full of surprises. One is that Paul Castellano is the least interesting character in the book. His power and majesty are declaimed and described but never shown to us by the authors. So it is very hard to understand why O’Brien and Kurins are willing to break so many rules for Castellano.

They arrest him in the Commission conspiracy case, allow him to change clothes and don’t cuff him in front of his family. They rush him to the Second Avenue Deli for a corned beef on rye in the hours between his booking and bail hearing. They offer him up to the courts but try their damndest to keep him away from the press.

The description of their merciful behavior toward him during his arrest is very affecting. His response--”I want you to know that I appreciate the way you’ve treated me”--is flat.

Much more interesting are the men of lesser influence. Gambino consigliere Joe Gallo appears throughout the book as a cynical seer, explaining, with a refreshing and radical anger, the profound corruption of our system.

The book is uneven, insightful and often entertaining, but it has many flaws. The authors accuse mobsters of murdering the English language. They themselves could at least be convicted of assault. The book builds to the bugging of Castellano’s inner sanctum, but it’s more than half over before the bugging is done, and it feels anticlimactic. The intensity and/or intelligence of the minor characters overwhelm the blandness of the Godfather on tape.

The book loses its narrative momentum over and over again, trying to tell too many stories that are never joined to the thin main thread. There is no structure to compensate. And the point of view doesn’t help. It seems to shift as much as the moral ground in this book.

The whole thing is a compelling mess. But some things just can’t be sorted out. How does one answer the central question that Joe Gallo puts to agent Andris Kurins: “Maybe you’re right to think that my way is bull . . . and maybe I’m right to think your way is bull. . . . But lemme ask you this, Andy. What if we’re both right? What then, Andy?”