For people who read a lot and have strong opinions about what they read (and, let’s face it, everyone who reads a lot has strong opinions about what they read), one of the pleasures of life is talking about what they’re reading. You know who they are. Or who you are. Hyperbole is never in short supply. “This is the greatest (or worst) book I’ve read this year” is a line as common as wronged women. For more nuanced critics (and every serious reader is a critic), there are references to a book being “not as good as x” or “better than y,” and of course it’s mostly subjective; there are few books universally acclaimed or despised.

When I pick up a book by someone whose work I’ve dependably enjoyed in the past, especially if it’s by a relatively prolific author, I pretty much expect to like it. Happily, I’m seldom disappointed, as good authors tend not to lose their talent and skill overnight, and the mediocre ones are not suddenly struck with the lightning bolt of creative genius.

As I was reading the new novel by John Lescroart, “Betrayal” (Dutton, 432 pages, $26.95), I thought that, for the first time with this fine writer, I might be disappointed. The book is billed as a Dismas Hardy and Detective Abe Glitsky novel and, inexplicably, for several hundred pages, they are nowhere to be found.

But that’s the thing with really good writers. When they do something unexpected, it’s often a good idea, and “Betrayal,” even without Diz and Abe, is still a terrific read, maybe the most exciting of all the books by Mr. Lescroart. It is reminiscent of several books by Nelson DeMille in that there is a spectacular legal thriller wrapped around a taut military action novel.

Diz Hardy agrees to take on some of the cases for a lawyer who has mysteriously disappeared. One of the cases involves Evan Scholler, a National Guardsman convicted of murdering Ron Nolan, an ex-Navy SEAL who was sleeping with his girlfriend. The two men had met while in Iraq. Since Mr. Lescroart is from the San Francisco area, it should be no surprise that there is a clear, left-wing, antiwar tone, and that these men perform acts for a corrupt organization and an equally corrupt government that may make up in efficacy what they lack in legality or even morality.

Scholler’s girlfriend had not responded to his last 10 letters, so Nolan — who was headed back to California — offered to deliver a letter for him. She’s gorgeous, Nolan (quelle surprise) falls for her, and that’s when the trouble begins. Scholler returns to America, learns of the betrayal, gets drunk, confronts Nolan, and blacks out, remembering nothing, including how Nolan got killed. The dubious jury convicts him. Though it is a seemingly open-and-shut case, Scholler’s lawyer nonetheless decides to appeal — and then vanishes.

For the final third of the book, Diz turns up and, aided by his friend Glitsky, discovers some things that will surprise the reader, and a couple that will be absolute knockouts.

These two series characters are always realistically well-drawn, which is why Mr. Lescroart has been a bestseller for the past dozen or so books. He had aspired to be a “literary” writer but, when that didn’t take, did a bit of slumming in the mystery world before realizing that he could combine the two, writing literary mysteries that satisfied both himself and readers.

In a profile of Dismas Hardy that Mr. Lescroart wrote earlier this year, he recalls the moment: “The inherent and irreconcilable dichotomy I had always perceived — maybe projected is a better word — between serious literature and the mystery genre vanished. I could tell an important story, perhaps even one containing a universal truth or two, and at the same time provide the kind of narrative drive that strong plot could guarantee, or at least facilitate. I could talk about moral and social and character issues — surely the provenance of serious literature — and write a fast-moving and entertaining story at the same time.”

Well, yes. Those of us who are serious aficionados of mystery fiction knew that. Mr. Lescroart brought to life a couple of characters in Diz and Abe whom we are always happy to encounter again — a difficult literary achievement. They have smaller roles than usual in the new book, but give it a try anyway. You won’t feel betrayed.

Mr. Penzler is the proprietor of the Mysterious Bookshop in Manhattan and the series editor of the annual Best American Mystery Stories. He can be reached at ottopenzler@mysteriousbookshop.com.