The cops in Joseph Wambaugh's new novel, "The Glitter Dome," have it tough. One pair falls asleep on a rooftop stakeout and wakes up covered with pigeon droppings. Another pair tries to break up a street fight between two male street hustlers, and one of the cops gets poked in the eye by a meddling gay-rights activist. One member of another team goes undercover at a massage parlor and responds prematurely to the ministrations of a masseuse. And a fourth pair has their hands full with a 6-foot, 6-inch transsexual who won't travel anywhere without a Dolly Parton wig. Compared to these guys, the beleaguered characters on "Hill Street Blues" have the easiest beat in town.

Wambaugh's beat is Los Angeles, where he spent 14 years as a policeman. His five previous books (four novels and one true crime account) are shot through with authentic detail and a genuine sympathy for the daily job pressures that often spill over, with disastrous consequences, into a policeman's personal life. A Wambaugh cop is often a walking time bomb, fueled by the violence and despair of the mean streets he walks, ready to detonate at any moment.

The four teams of police detectives in "The Glitter Dome" all work hard to keep from detonating in the wrong person's face. Three of the teams -- the narcs Weasel and Ferret, the homicide crewcut cops Schultz and Simon, and the black-and-white pair of reckless "street monsters" Buckmore Phipps and Gibson Hand -- are familiar caricatures from other popular books, films and TV shows about police work. Al Mackey and Martin Welborn are the real flesh-and-blood characters, both of them given to serious doubts about the kinds of compromises they make every day to keep their heads above water.

"The Glitter Dome" (the title refers to an off-duty cops' hangout, where the bartender shortchanges the willing patrons and the cop groupies ply their trade) is set in Hollywood. Not the Hollywood of glamor and fame, but "the Boulevard," where the street action never lets up. The fact is, as Wambaugh quickly points out, most of the captains and kings of the film industry wouldn't be caught dead in Hollywood proper.

Except for one. Nigel St. Claire, the president of the film division of a major (unnamed) studio is found murdered in the parking lot of a (gasp!) bowling alley on Sunset Boulevard. After Schultz and Simon are unable to crack the case, it's handed over to Mackey and Welborn, who, fresh from a bad night at the Glitter Dome, are in no mood to take on any seemingly unsolvable homicides.

This is not, however, a tightly plotted mystery novel. Wambaugh is much more interested in diverting his readers with little asides about police work, the current state of the film industry, and the escapades of the three other teams. The broad and often black humor that infuses this book will remind Wambaugh fans most of his novel "The Choirboys," although Wambaugh keeps a tighter rein on the proceedings this time around.

Wambaugh seems to enjoy leading readers down blind alleys by introducing characters who simply don't matter much to the story, or setting up expectations that are neatly reversed. In the opening chapter, set at the Glitter Dome, Al Mackey seems to be on the ropes, but by the novel's end, it is his partner Martin Welborn who is unable to cope with the real-life demons he encounters in his job. In between, the two interview what might be called a cross section of Hollywood low and near-low life in search of St. Claire's killer, from a young marine who does street hustling on weekends to an alcoholic cinematographer who's taken up skating for his health to a teen-age prostitute who may be in over her head when she screentests for a film to be made in Mexico. It's that aborted film project, plus other dirty business, that leads Mackey and Welborn to the killer.

But Wambaugh is too clever to reveal whodunit at what seems to be the right moment. When the evidence points in one direction, the detectives are stymied, so they find themselves a killer to make a deathbed confession. Close of case, right? Not quite. The conclusion of "The Glitter Dome" is the literary equivalent of a one-two combination that leaves the reader reeling.

This novel is a slick piece of entertainment, but like all of Wambaugh's books, it raises the question of which side of the law cops work. All eight characters, particularly the "street monsters," one of whom asks to be assigned to surveillance detail because it gives him the opportunity to kill people, play games with the law, sometimes out of desperation over procedures that hamstring them, sometimes because they don't give a damn. These are the most chilling parts of the novel, when the question of who's protecting us from the cops arises. Wambaugh doesn't have the answers. As long as he sets his cops amid the pathetic and despicable, the cops will still come out ahead, if only by default.