“Brutality,” by Ingrid Thoft. G.P. Putnam’s Sons, New York, 2015. 452 pages. $26.95.

The young and successful Boston private investigator Fina Ludlow has found an M.O. that works wonders. She pesters people till they crack. It’s a sensible device that relies heavily on energy and persistence.

When combined with some smart detection and the rush that junk food and diet cola pumps out, you’ve got a winning formula. As for the brutality mentioned in the title of Ingrid Thoft’s newest P.I. procedural, it’s more about Fina’s relentless questioning than the nature of the crime she’s charged with solving. People, plagued by Fina, spill everything in desperation.

In “Brutality,” a former college soccer star, Liz Barone, sues her alma mater after being diagnosed with a degenerative brain disease due to her sports-related head injuries. When she’s discovered on her kitchen floor with a massive head wound, Liz’s mother hires Fina to find out who did this.

Fina quickly turns up a good number of suspects — all unlikeable and, unfortunately, uninteresting. There’s the scientist who heads the lab where Liz worked. He is angry because Liz may have been the reason they were passed over for a valuable grant. The head of the development department at Liz’s former college and Liz exchanged some possibly incriminating correspondence.

And Kevin, the most likely suspect, has a volunteer position as a super-booster of the athletics programs at the college. He and Liz had some kind of long-term friendship begun in college and her lawsuit poses a serious threat to the school and the athletics programs. Other suspects and other crimes emerge as the story blossoms.

Adding to the intrigue are Fina’s reprehensible parents. Her handsome, powerful father runs a very successful personal-injury law firm and two of her brothers work with him. Fina prefers being a personal investigator; it suits her skill set and allows her some autonomy from her controlling father.

Her mother is probably the other reason this book is called “Brutality.” She’s emotionally brutal to Fina. As a result, Fina has found and nurtured a relationship with an older couple who feel more like parents to her.

Add to this intrigue a car bomb that nearly incinerates Fina and one of her brothers. Then there’s a vile brother living down south who sexually abuses girls, including his teenage daughter who now lives in Boston with one of her lawyer uncles. Topping off the persons of interest is Fina’s on-again, off-again lover, a police detective and his severe boss.

One of the most interesting storylines in the book is Fina’s working relationship with the police. Private investigator and police are both looking for the same murderer. When and why Fina decides to share her findings with the police is explained as the story moves forward. That Fina feeds the cops more than they feed her could endanger the love-interest angle, but Cristian seems to have a strong ego equal to that of Fina.

What’s fun about Fina is how much she relishes people’s growing anger and frustration with her as she burrows ever deeper into their lives. The meaner they get, the better. As far as Fina’s
concerned, she’s getting to them. Sooner or later they are going to cry out for mercy.

The first problem with this book is that the central mystery — a soccer mom and former soccer player gets a head injury in the kitchen — lacks drama. The second problem is that Fina’s tactic of questioning and re-questioning people of interest means we are there, too, enduring the multitude of endless queries that seem to yield little that’s new.

OK. These are not necessarily questions seeking revelatory new material. They are, in part, meant to wear people down. Sadly Fina is brilliant at that.

Fina is an excellent protagonist with good baggage. She’s potentially fascinating. She just needs better crimes and more suspense if she wants readers to care along with her.

Rae Padilla Francoeur’s memoir, “Free Fall: A Late-in-Life Love Affair,” is available online or in some bookstores. Write her at rae.francoeur@gmail.com Read her blog at freefallrae.blogspot.com or follow her on Twitter at @RaeAF.