At the start of “Gray Mountain,” John Grisham’s angry and important new novel, Samantha Kofer — age 29, Washington native, graduate of Georgetown and Columbia Law — is a third-year associate at a huge New York law firm. She works 100 hours a week, doing boring chores that she hates, but she’s earning $180,000 a year and expects to be a $2 million-a-year partner by age 35.

Or she did expect that, until September 2008, when the economy tanked and panicked law firms began ridding themselves of associates and partners. We meet Samantha at the moment — “day ten after the fall of Lehman Brothers” — when the ax falls for her, with only one consolation offered. If laid-off associates will agree to intern with a nonprofit agency, they can keep their health benefits and will be considered for rehiring if prosperity returns. Thus it is that Samantha finds herself at the Mountain Legal Aid Clinic in tiny Brady, Va., in the heart of Appalachia.

That opening scene, wherein a world of privilege abruptly vanishes for astonished young people who have known only success, is startling, but no more than Grisham’s portrait of the world of poverty and injustice that Samantha soon enters. The author does justice to the physical beauty of Appalachia and to the decency of most of its people, but his real subject is the suffering inflicted on those people by mining companies and politicians who pander to them.

Samantha’s new boss, Mattie Wyatt, has kept the Mountain Legal Aid Clinic alive for 26 years. The first case she assigns to Samantha is that of a woman who needs protection from a husband who deals in crystal meth and beats her. Then Samantha moves on to her first black-lung case. If miners can prove they’ve been disabled by years of breathing coal dust, they’re entitled to payments that can reach $1,000 a month. The problem is that Big Coal employs hordes of lawyers to delay cases until the miner dies or gives up, and the lawyers are often backed by doctors, prosecutors, judges and regulators who are in bed with the coal companies. Mattie warns that only 5 percent of miners with black lung receive benefits. That doesn’t stop Samantha from championing one dying miner — and learning how heartbreaking that can be.

Mattie has a nephew, a good-looking young lawyer named Donovan Gray who’s pursuing a one-man crusade against Big Coal. Grisham dramatizes two of his cases in detail. Both involve the form of strip mining often called mountaintop removal. It’s cheaper for mining companies to remove the tops of mountains — hundreds of feet of earth and rock — and mine exposed seams of coal than to dig for it underground. This rape of the mountains does terrible harm — collateral damage, one might say — to streams, valleys and human beings so unlucky as to be below those mountains.

“Gray Mountain” by John Grisham. (Doubleday)

In one of Donovan’s cases, a bulldozer working atop a mountain dislodged a six-ton boulder that tumbled down for more than a mile before it crushed a house trailer where two boys were sleeping. On behalf of the boys’ parents, Donovan has brought the case to trial and is asking for an unprecedented judgment of $3 million. The worried coal company, as the trial nears, offers a $1.5 million settlement, but Donovan — against the advice of friends — insists on taking his chances with the jury. It’s an agonizing wait for the jury’s decision.

In another case, Donovan has obtained — stolen, actually — documents proving that a mining company knew that chemicals it used in mountaintop removal have for a decade been polluting the wells of a small town nearby, giving it one of the highest cancer rates in America. The documents prove the company made a cold economic decision that fighting lawsuits would cost less than trying to clean up its lethal mess. Donovan hopes to introduce the purloined papers in his suit against the company; the company, for its part, has enlisted a friendly U.S. attorney and the FBI to recover the papers and perhaps prosecute the crusading lawyer. Samantha, to her horror, finds herself embroiled in this battle.

As Grisham’s story unfolds, an important figure dies, perhaps murdered. Samantha is followed by thugs who seek to intimidate her. Undaunted, she finds time for a taste of romance. We encounter unexpected bits of humor here, of sociology there. Finally, the question is whether Samantha will return to the glories of New York or stand and fight amid the hardships of Appalachia.

Grisham makes his characters all too real, but the heart of his story is his relentless case against Big Coal. We all know something about the plight of miners, but we are unlikely to have encountered the realities of their lives in the depth provided here. This is muckraking of a high order. If it’s possible for a major novelist to shame our increasingly shameless society, “Gray Mountain” might do it. This novel, following “Sycamore Row” (2013), a searing look at racism in his native Mississippi, shows Grisham’s work — always superior entertainment — evolving into something more serious, more powerful, more worthy of his exceptional talent.

One hopes Grisham’s recent, muddled comments on child pornography won’t detract from the achievement of this book. Writers do well to send their well-wrought fictions forth into the world and leave the temptations of off-the-cuff sermonizing to political candidates and other desperate characters. The novel will outlive the controversy.

Anderson regularly reviews mysteries and thrillers for Book World.

GRAY MOUNTAIN

By John Grisham

Doubleday. 368 pp. $28.95