The Running Grave by Robert Galbraith
The Manor House by Gilly Macmillan
The Exchange: After the Firm by John Grisham

Consider this column a mystery trick-or-treat bag, replete with big books about such scary subjects as cults, international terrorism, and the dangers of winning the lottery. The bag needs a reinforced bottom to accommodate J. K. Rowling’s seventh Cormoran Strike novel, written under the pseudonym Robert Galbraith; in the past few years, installments of this series have expanded enough to make Karl Ove Knausgaard’s output look puny.

The Running Grave’s 945 pages may seem daunting, but fans will embrace this opportunity for complete, pleasurable immersion in the complicated and sometimes perilous lives and cases of private detective Cormoran Strike and his partner, Robin Ellacott. (Strike was an army intelligence officer who lost a leg in Afghanistan, then set up shop as a private investigator in London. Like many an old-school detective, he lives above his office, where he handles cases with Robin, who graduated from temp receptionist to partner.)

The cult at the center of the novel, the Universal Humanitarian Church, considers itself a religion with the modest goal of ending poverty and uniting all cultures while guiding its members to “pure spirit” level. The U.H.C. puts up a shiny, happy front, with a charismatic leader, fundraising for the disadvantaged, celebrity members, and attack-dog lawyers who kill bad publicity.

How dangerous it may be is what Strike needs to find out after Sir Colin Edensor approaches the agency about the possibility of extracting his adult son, a church member who broke off all contact with his wealthy family five years earlier to live at the cult’s farm in Norfolk. Strike wants to send one of his people undercover to the farm as an aspiring member, and Robin volunteers, assuming a new look and identity. But once at the farm, she finds herself up against the cult’s cruel methods of coercive control. Physically and mentally depleted, Robin nonetheless digs into the church’s history, looking for information that could crack its façade.

The narrative alternates between Robin’s harrowing impostor act at the farm and the agency’s more routine investigations back in the real world, as well as Strike’s personal travails. Plot-wise, the bread-and-butter cases may seem superfluous, but they serve as relief from the fear and tension of the cult sections. Rowling’s storytelling remains impressively strong throughout—her ability to compel interest through this long and winding tale is superhuman. And those invested in the progress of Robin and Strike’s long-repressed attraction to each other can take heart—that needle shows infinitesimal signs of moving.

If you want to brush up on the canon before diving into The Running Grave, there’s a BBC adaptation called C.B. Strike that’s pretty close to ideal, largely because of Tom Burke and Holliday Grainger as Strike and Robin, an intensely simpatico duo with chemistry to burn.

As the Harry Potter movies showed, Rowling’s visually oriented style and Dickensian knack for eccentric characters make her work a natural for the screen, though it took a few seasons to settle into the right mode. The Strike books are well served by the show’s slightly retro look and mood. Instead of the aerial-drone footage of London’s glassy, thrusting skyline that defines the look of so many police procedurals, the camera mostly remains at street level, jostling along funky Denmark Street in Soho, where Strike’s office is tucked in among music stores, comic-book shops, and ethnic restaurants. It’s a place you want to get lost in.

Cults and con artists have a lot in common. Both isolate their victims from friends and family, gaslight them, limit their choices. I won’t give away how that dynamic plays out in English writer Gilly Macmillan’s The Manor House, but it’s deliciously clever.

J. K. Rowling’s storytelling remains impressively strong throughout The Running Grave—her ability to compel interest through this long and winding tale is superhuman.

Tom and Nicole Booth are a lower-middle-class couple who have done the impossible—they won a ton of money in the lottery and didn’t blow it on stupid stuff. Aspirational Nicole had long nursed a fantasy about building a beautiful glass house near a nature preserve she visited as a child. With their winnings, Ms. Booth builds her dream house and christens it the Glass Barn.

But everything turns to ash when she returns home one afternoon to find her husband floating face down in their swimming pool. She runs to the nearest house for help, and the police are summoned.

Grief-stricken Nicole needs a friend, and her glamorous neighbors Olly and Sasha, who occupy the sprawling, historic Manor House with their oddly subservient housekeeper, are only too happy to help. As is Tom’s old friend Patrick, a feckless hothead who offers to stay with Nicole. But nothing and no one are as they seem, and since the police can’t seem to get a fix on their suspects, it’s down to Nicole to separate illusion from reality.

Macmillan uses multiple shifts of time and perspective to propel this unpredictable story; your attention won’t flag for a minute, thanks to her nimble inventions, and the double twist at the end is a killer.

Nothing and no one are as they seem in Gilly Macmillan’s The Manor House.

The much-vaunted return of Mitch McDeere, some 15 years after his appearance in John Grisham’s benchmark legal thriller The Firm, is a bit of a disappointment on its own terms, but for anyone dying to know what happened to Mitch and his wife, Abby, after escaping from the meltdown of the corrupt Bendini law firm, The Exchange delivers.

Grisham sets the sequel in 2005. Mitch is now a partner at Scully & Pershing, the largest law firm in the world, headquartered in Lower Manhattan. He and Abby, who’s a cookbook editor, live an idyllic life on the Upper West Side with their twin sons.

There’s a lot of catch-up at the beginning, much of it meant to establish Mitch as a decent guy despite his privilege—he reconnects with a former Bendini colleague who did prison time and signs on for a pro bono death-penalty case, among other good-ish deeds.

But the premise is a grabber. Luca Sandroni, who heads S&P’s Italian office, has been hired to bring a lawsuit against the Libyan government on behalf of a Turkish construction company that’s owed $400 million for its work on a crackpot bridge project dreamed up by Muammar Qaddafi. When it became an embarrassment, Qaddafi walked away from it, leaving behind a massive debt to the Turks.

The premise of John Grisham’s The Firm sequel is a grabber.

Sandroni is ill, so he entrusts the case to Mitch, with the request that his daughter Giovanna, a young S&P associate in London, assist him.

Things go horribly wrong when Giovanna is kidnapped by terrorists in Libya and Mitch has to step up as the point man in the effort to raise the ransom for her safe return. Since the governments involved don’t like to give money to terrorists and S&P doesn’t have extra millions lying around, Mitch and his team scramble all over the world for other ways to get it as the clock ticks down.

It should be exciting, but somehow the suspense dissipates in the second half, with too much focus on fruitless meetings and the hazards of giant bank loans.

Mitch doesn’t develop much as a character, and his emotional temperature is pretty cool for someone in such fevered straits. Even Abby, who gets dragged into the nightmare, seems remote, noting appreciatively what a good airline British Airways is on her way to a dangerous rendezvous. It reads like product placement.

Maybe it seemed like a good idea at the time, but it’s possible Grisham’s heart just wasn’t in the resurrection of Mitch McDeere.

Lisa Henricksson reviews mystery books for Air Mail. She lives in New York City