John Grisham is one of this country’s best-selling novelists — and he is also an important social critic. In more than 30 novels, he has often used his exceptional storytelling skills to take a hard look at injustice and corruption in the legal world and in our society as a whole.

His first novel, “A Time to Kill” (1989), written when he was a young lawyer and state legislator in Mississippi, was a searing look at Southern racism, as a black man went on trial for killing two men who raped his daughter. In “Sycamore Row” (2013), he brought back Jake Brigance, the lawyer-hero of “A Time to Kill,” to represent a black housekeeper who had been willed $20 million by a white man she nursed as he lay dying; this time Brigance was fighting not rapists but respectable citizens who intend to relieve the housekeeper of the fortune. In “Gray Mountain” (2014), an idealistic young lawyer joins a legal clinic in the Appalachian coal country and learns how cruelly the mining companies cheat their workers and despoil the land.

"The Whisperer," by John Grisham (Doubleday)

His new novel, “The Whistler,” is another ambitious look at corruption, this time involving a judge. The story begins with two investigators, Lacy Stoltz and Hugo Hatch, who work for the Florida Board on Judicial Conduct, which polices judicial misbehavior. They are approached by a whistleblower, a disbarred lawyer, who asks if they want to investigate “the most corrupt judge in the history of American jurisprudence.”

He points them toward a Native American-operated casino in the Florida Panhandle that takes in a half-billion dollars a year in cash and a ruthless gangster whom the Native Americans fear. When some members of the tribe opposed the casino, the gangster had them killed. Now he shares the profits with the tribe’s leaders and they’re all protected against legal challenges by a corrupt state judge. Each month the gangster takes the judge a briefcase containing $250,000 in cash; this has been going on for 11 years.

The FBI, busy with its pursuit of terrorists, shows no interest in the corrupt casino. The two investigators thus proceed on their own, knowing their inquiry may be dangerous. “We’re not cops with guns,” Lacy says. “We’re lawyers with subpoenas.”

Her concern is justified. One person is soon murdered, one is badly injured and another goes missing. We meet a Native American on death row who was convicted of murder on perjured testimony. The FBI eventually enters the case, and Lacy, who’s 36, single and attractive, enjoys a cautious romance with one of the agents.

Although “The Whistler” reads as first-rate fiction, it takes on the feel of a documentary as Grisham’s complicated crime unfolds in great detail. The Native Americans, inundated with cash, face unforeseen dangers. The gangster, who has advanced from dealing cocaine to leading a criminal empire, thinks himself untouchable. The judge glories in her ill-gotten wealth:

“She went to her vault and spent a few moments admiring her ‘assets,’ goodies she’d been collecting for so long that she now believed she deserved them. Cash and diamonds in small, portable, fireproof safes. Locked, steel cabinets filled with jewelry, rare coins, vintage silver goblets and cups and flatware. . . . All of it had been acquired by casino cash, skillfully laundered.”

She’s supremely confident, sure she’s above the law — because she is the law.

But inevitably the wheels of justice begin to turn. This is after all a Grisham novel, and the story winds down with the kind of legal drama readers have come to expect from him.

Best-selling novelist John Grisham (Billy Hunt/Billy Hunt)

In a recent interview with Entertainment Weekly, Grisham quipped that while he was writing this book, his wife had asked him to get off his soapbox. Readers can be grateful that he didn’t heed that advice. “The Whistler” is a fascinating look at judicial corruption — an entirely convincing story and one of Grisham’s best.

I can’t think of another major American novelist since Sinclair Lewis who has so effectively targeted social and political ills in our society. Lewis’s scathing portraits of our Main Streets, Babbitts and Elmer Gantrys won him the Nobel Prize for Literature in 1930. In Grisham’s case, it is time at least to recognize that at his best he is not simply the author of entertaining legal thrillers but an important novelistic critic of our society.

Patrick Anderson regularly reviews mysteries and thrillers for The Washington Post.

the whistler

By John Grisham

Doubleday. 374 pp. $28.95