The subtitle of "Long Haul" is "Hunting the Highway Serial Killers," but that's not what it's really about. Or, at least, not all of the time.

Frank Figliuzzi's book is best when it listens to its subtitle. The former Federal Bureau of Investigation assistant director introduces us to a special FBI unit that, since 2004, has linked more than 850 killings to long-haul truckers. It's shocking to find out that there are so many murders believed to have been committed by truckers and to realize that the problem is grave enough for the FBI to have doubled down on it by creating the Highway Serial Killings Initiative.

Figliuzzi is quick to point out that the vast majority of truckers are law-abiding folks whose difficult work keeps this country running (as we learned, sometimes painfully, when the COVID pandemic interrupted their labor). But "Long Haul" also gets at the unique aspects of the job that can make its practitioners turn violent: loneliness, sometimes-shadowy regulation, unhealthy hours (and the drugs that may fuel them) and more.

All of which leads Figliuzzi, who leans toward the melodramatic even when he's not discussing serial killers, to write, "Let me say that again: There is enough evidence of similarities among different clusters of killings for the FBI to say with confidence that there are multiple homicidal maniacs on our nation's highways."

That could definitely give you pause next time you consider flipping off a trucker who makes it difficult to pass on the freeway.

"Long Haul" contains fascinating information on how some killers have been tracked down, using methods that range from the latest in high-tech criminology to clues left carelessly behind. (One murderer's name and phone number were conveniently found in a jacket on the corpse of his victim.)

There would seem to be plenty of information here for a true-crime stunner along the lines of Robert Kolker's "Lost Girls." But Figliuzzi muddies "Long Haul" by including chapters in which he drives along with a (law-abiding) truck driver, detailing their not-scintillating efforts to load and unload flatbeds. He also delves into the psychology of sex workers who hang out at truck stops, a little-explored subculture that merits its own book.

Readers may also be vexed by Figliuzzi's methodology. The three most-quoted people in "Long Haul," two truckers and a sex-worker-turned-counselor, use pseudonyms. Other sources aren't named at all. That's frustrating for the reader and was frustrating for the writer, too, I'll bet. It made me curious at what point in the week they spent together that a trucker whose real name is not "Mike" insisted on anonymity.

In other words, I spent too much of "Long Haul" wondering about the story behind the story. Figliuzzi has spotlighted a fascinating world that I knew nothing about, and I'm grateful for that. I just wish all of his sources had been with him for the long haul.

Long Haul

By: Frank Figliuzzi.

Publisher: Mariner, 256 pages, $25.99.