When Honor and Justice Were Things to Be Cherished : PRONTO, <i> By Elmore Leonard (Delacorte: $21.95; 265 pp.)</i>

Elmore Leonard begins his 31st novel with a Miami bookmaker, Harry Arno, about to tell his girlfriend Joyce his biggest secret. But she already knows it: When he was stationed in Rapallo, Italy, during WWII, he shot a deserter. The joke, and the setup for the novel, is that Harry doesn’t realize that he has talked about his “secret” often--whenever he’s had too much to drink. And when the FBI, out of perversity, puts him on the spot with Mafia boss “Jimmy Cap” Capotorto, forcing Harry to hop it to his special Italian hideaway, everybody knows where he is.

Maybe not everybody. But Raylan Givens, the U.S. marshal responsible for keeping track of Harry, knows. And so does Tommy Bitonti, a.k.a. Tommy Bucks or the Zip, a hit man of the old Sicilian school who believes that the new Mafiosi, Jimmy Cap included, are a bunch of wusses. The stage is thus set, admirably, for another of the author’s stylish, darkly funny confrontations between a laid back but quirky professional, Givens, and a street-smart but equally quirky sociopath, the Zip. The fact that Harry, the man they’re determined to help and harm, respectively, is a selfish, insensitive, essentially worthless lout does nothing to alter the intensity of their dedication.

It’s a mistake to categorize Leonard’s novels as mysteries or thrillers. Murderers are not announced in their final chapters, secrets are not revealed, the fates of nations do not hang on their outcome. They are tales of heroes and villains engaged in mortal and moral struggle. What distinguishes them is Leonard’s ability to create characters, conversations and situations that are as natural and convincing as they are unique. He seems to know the hustlers, con men, killers and especially the good guys firsthand, and he passes along this knowledge in an understated way that suggests we readers are his equals in awareness.

Here, for example, is Raylan Givens explaining himself to Nicky Pesta, a Miami punk whom the Zip has sent to kill him: “Mr. Zip . . . offered me money--did he mention that to you?--30 million lire, which sounds like a lot more’n it is, if I’d go away and quit bothering you people. To me, that was an insult. Not the amount, you understand, but that he’d entertain the idea I might take it. A man like him thinking everybody has a price. Well, there was a time he could’ve had me for $15 a day--hell, less than that--when I was a boy working in the coal mines. Anybody ever asked what was my price, that would’ve been it, 15 a day. I’ve worked deep mines, wildcat mines, I’ve worked for strip operators, and I’ve set out over a year on strike and seen company gun thugs shoot up the houses of miners that spoke out. They killed an uncle of mine was living with us, my mother’s brother, and they killed a friend of mine I played football with in high school. This was in a coal camp town called Evarts in Harlan County, Kentucky, near to 20 years ago. You understand what I’m saying? Even before I entered the Marshals Service and trained to be a dead shot, I’d seen people kill one another and learned to be ready in case I saw a bad situation coming toward me. . . . In other words, if I see you’ve come to do me harm, I’ll shoot you through the heart before you can clear your weapon. Do we have an understanding here?”

It should be noted that Leonard began his career as an author with yarns about cowpokes and villains. His 1981 contemporary police novel, “City Primeval,” was constructed very much like a Western, complete with shootout in the street; and in case the point was not made, it carried the subtitle “High Noon in Detroit.” This new book, with its thoughtful, mild-mannered lawman protagonist looking a bit silly and out of place in Italy wearing his Dallas special Stetson (think Joel McCrea in his prime), is another of his wild West/urban crime melds. It mixes the romantic notions of the past, when honor and justice and a woman’s love were things to be cherished, with Leonard’s particularly adroit insight into the harsh realities and tensions of today. The mixture works beautifully.