What fan of hard-boiled detective fiction hasn't imagined himself in the gumshoes of his favorite private eye, cracking wise while cracking bad guys' skulls? Mark Schorr's fictional New York cab driver Simon Jaffe indulged in such fantasies to escape from his dull existence until he actually succeeded -- losing his own identity to become Red Diamond, ace private investigator.

Jaffe's alter ego is no ordinary shamus. He can "outpunch Mike Hammer, outdrink Nick Charles, outsleuth Sam Spade, outshoot Race Williams, outwisecrack Philip Marlowe, outstud Shell Scott, outbench-press Spenser." Credentials like these make Diamond the perfect vehicle for Schorr's ingenious and affectionate parodies of hard-boiled literature, the third of which -- "Diamond Rock" -- has just been published.

In 1983's "Red Diamond: Private Eye," Jaffe plunged into a trancelike depression when his wife sold his beloved collection of detective novels and pulp magazines. When he finally emerged, three people were dead in a Times Square flophouse and the meek cabbie had been transformed into Red Diamond, his favorite pulp tough guy. Despite living in a fantasy world of 1940s fictional private investigators and their exploits, Diamond managed to thwart some 1980s crooks in the Big Apple and Los Angeles with hard words and harder fists -- and occasionally his .38.

This unique premise works wonderfully, largely because Schorr depicts Diamond as a sort of street-smart Don Quixote, an anachronism whose tilting at windmills yields hilarious results. Diamond's dogged pursuit of his archenemy Rocco Rico -- whom he suspects of masterminding every shady deal that goes down -- and his desperate search for his long-lost girlfriend Fifi La Roche -- for whom he mistakes nearly every blond he meets -- supply a steady stream of laughs throughout the novel. Knowing that Diamond will never find either Fifi or Rocco, since they are characters from Jaffe's pulps, only adds to the reader's amusement. Schorr sustains the same high level of humor in his second novel, "Ace of Diamonds," as well as in the current book.

An equally rich source of fun are Diamond's own, highly distinctive accounts of previous cases he's handled, which Schorr alternates with a third-person narrative describing the private eye's current doings. In these first-person sections, ostensibly from the cabbie's favorite pulps but actually from Schorr's fertile imagination, the author pays homage to tough-guy writing while he gently mocks it. Consider this excerpt from "Diamond Rock":

"The shop was a gavel's throw from the courthouse, filled with the usual types you find in the court system shadows. Hustling bail bondsmen, ambulance-chasing attorneys, cops who could be bought for the price of a lunch, and judges who cost at least a dinner.

"I opened the door and let in a biting blast of Lake Michigan air. The joint could use it. It smelled of old cooking oil, stale cigars, and corruption.

"I unbuttoned my trenchcoat and patted the roscoe slung under my shoulder. It was cold and hard, like the pavement where Bucky the newsboy lay. He was a good kid, caught in the mob's crossfire.

"Rocco Rico was behind the lead. It was meant for me. I'd been lucky. Bucky hadn't been. A tough little thirteen-year-old supporting his crippled mother and blind sister."

Passages such as this, animated by the author's intentional exaggeration of hard-boiled slang and cliche's, abound in each of the novels. Frequent references to well-known fictional private eyes, spiced with Diamond's revisionist accounts of some of their most famous cases, provide extra treats for aficionados of the genre.

"Diamond Rock" takes our hero to both coasts again, as he investigates a New York mobster's finances and agrees to look after members of a rock group in L.A. who have been receiving threats. In an unexpected development, Diamond's life as Jaffe intrudes on his detective work for the first time in the series, as his son persuades him to help find his runaway sister and accompanies Diamond on his sleuthing.

Despite the addition of this paternal motivation for the private eye, "Diamond Rock" is no less lighthearted or funny than its predecessors. Its humor remains fresh and original, as Schorr concocts seemingly endless and equally entertaining variations on the same themes that produced so much mirth in "Red Diamond: Private Eye" and "Ace of Diamonds."

Readers who love hard-boiled detective fiction will most likely enjoy the Red Diamond books as knowing and loving tributes to the genre. Others, who might not know a Hammer from a Spade, should still recognize this Diamond as a gem in his own right.