The crime novel has become increasingly popular in recent years. The major element that most clearly distinguishes this subgenre from the rest of mystery fiction is that there is, in fact, no mystery. It is a depiction of criminal life, told from the viewpoint of the criminal. It is not very much a “whodunit” but more of a “whydunit.”

STRUCTURE There are various forms of the crime novel, some very dark, some humorous. In one type of book, a criminal sets a career path and decides to become a burglar or a gangster. In another, the primary focus is the analysis of a psychopathic or antisocial figure.

In its earliest form, the crime story was about Robin Hood figures or bandits. These were refined to become stories about gentlemen crooks, epitomized by E.W. Hornung’s Raffles, the amateur cracksman, and other charming rogues who mainly stole from people who seemed to deserve it. It was common for these shady characters eventually to go to the other side and either detect crime or prevent it.

With the rise of organized crime in America, gangster stories became both possible and popular. People wanted to read about Al Capone and John Dillinger, whether in the daily newspaper or in idealized fictional form. In later years, Mario Puzo’s “The Godfather,” an apparently realistic (although completely fictional) depiction of life within the Mafia, became the best-selling crime novel of all time.

Noir fiction, too, spoke to a nation beaten down by the Great Depression. This opened the door for James M. Cain, Horace McCoy, and their nihilistic comrades, joined in later years by Jim Thompson and his vicious killers and Elmore Leonard and his charming ones.

HOW TO TELL Certain titles or dust-jacket descriptions are obvious. When the focus is on a robbery, a caper, or some other illegal activity, and not on anyone whose job it is to solve or prevent it, the book is clearly a crime novel. Often, in spite of horrific events on either a massive scale or a personal one, the author does not attempt to make any moral judgment. Many authors refuse to be regarded as a mystery writer rather than one who merely desires to examine criminal themes. Detective fiction has stringent moral values and tends to be philosophically conservative; crime fiction tends to be radical, or at least anti-establishment.

THE BEGINNING Such mainstream novels as “Les Miserables” and “Crime and Punishment” have little to do with detective fiction, even though they feature hardworking, relentless policemen. We know who did it. The question is why they did it and what effect it had on them. If one wants to stretch a point, the first crime story occurs in the first book of the Bible, when Cain murders his brother, Abel. A rich history of crime fiction persists through the ages from “Oedipus Rex” to “Macbeth” to almost all the major works of Charles Dickens.

THE GREATS James M. Cain exemplifies one type of crime fiction. In such novels as “The Postman Always Rings Twice” and “Double Indemnity,” passion overcomes reason, and unappealing people plot murders for sex or money or both. This is a common theme of classic noir novels and the films made from them, such as Geoffrey Homes’s “Build My Gallows High” (filmed as “Out of the Past”), Richard Stark’s “The Hunter” (filmed as “Point Blank”), and Patricia Highsmith’s Ripley series (notably “The Talented Mr. Ripley”).

Other popular crime novels show criminals planning and executing robberies. W.R. Burnett’s “The Asphalt Jungle” and “High Sierra” are examples, as are Jim Thompson’s “The Grifters” and Lionel White’s “Clean Break” (filmed as “The Killing”). While these books are dark, the same structural elements may appear in comic novels, usually capers, such as Eric Ambler’s “The Light of Day” (filmed as “Topkapi”) and Donald E. Westlake’s always humorous works, notably those about John Dortmunder and his gang (“The Hot Rock,” “Jimmy the Kid,” and “Bank Shot”).

Naturally, prison and gangster stories – including such famous novels as Burnett’s “Little Caesar,” Puzo’s “The Godfather,” and McCoy’s “Kiss Tomorrow Goodbye” – fall into the crime-novel category. Stories featuring psychopaths are related, too: The best include John D. MacDonald’s “The Executioners” (filmed as “Cape Fear”), Highsmith’s “Strangers on a Train,” and Davis Grubb’s “Night of the Hunter.”

TODAY’S BEST Mr. Leonard tops any list of writers about criminals, both petty and major. While the brilliant Thomas Harris can’t be ignored because of his creation of Hannibal Lecter, his books are mainly told from the point of view of the FBI agents who hunt “the Cannibal” and his idolators. Mr. Westlake continues to write the funniest crime capers of all time.

Lawrence Block’s Bernie Rhodenbarr series features his activities as a burglar, though he spends a lot of time solving crimes, too. His hit man, Keller, is a different story, with a character as amoral as Highsmith’s Thomas Ripley. While James Ellroy writes about cops, particularly in Los Angeles, so many corrupt and violent characters populate his works that they seem closer to the crime novel than to mystery fiction. And no one has written better prison fiction that Eddie Bunker (“No Beast So Fierce,” “The Animal Factory”).

The constraints of the detective story have become less appealing to a large number of readers, as well as to writers who find the form difficult. So it is safe to say there will be much more crime fiction on the horizon in the years ahead – for better or worse.

Next week: The thriller.

Mr. Penzler is the proprietor of the Mysterious Bookshop in Manhattan and the series editor of the annual “Best American Mystery Stories.” He can be reached at openzler@nysun.com.