When Book World put me on the thriller beat a couple of years ago, most of my reading in the genre had been books by its best-known practitioners, people like Michael Connelly, Elmore Leonard, John Sandford and Thomas Harris. The great pleasure of the assignment has been discovering -- and telling readers about -- how many other people who are highly talented, if less well known, are currently writing in the genre. I don't know a better example than John Lescroart, whose legal thrillers are pretty much state of the art today.

Lescroart (it's pronounced Les-kwah) is an old-fashioned novelist, in the best sense of the word. His plots are excellent, but the great strengths of his work lie in his characterizations and in his ability to set his legal battles in a rich and believable world. Lescroart has published 13 novels, and almost all of them concern two old friends, Abe Glitsky and Dismas Hardy. They once were young San Francisco policemen together. But now Glitsky is the city's chief of detectives and Hardy is a defense lawyer, which means that Glitsky is often trying to put someone in jail whom Hardy is fighting to keep out of jail. Their friendship, often tested, somehow survives.

Glitsky is a hard case -- "half black and half Jewish and every inch of him scary looking" -- while Hardy is more the romantic. He advanced from the police force to law, but "when his first marriage broke up in the wake of the accidental death of his son, he took close to a dozen years off to tend bar and contemplate the universe through a haze of Guinness stout." Eventually, Hardy sobers up, marries the admirable Frannie and reluctantly returns to the law because he needs the money.

Hardy doesn't want to defend guilty people, so he tries to avoid criminal law, but he keeps getting sucked into it. In The Mercy Rule, he defends a young man charged with killing his father. He is a likable young man, and we more or less believe he's innocent, but in truth neither Hardy nor the reader really knows who killed the old man. So part of the drama is whether or not Hardy can convince a jury that the young man is innocent, and another part, regardless of what the jury does, is finding out what really happened. On both counts, Lescroart does not disappoint.

But much more is going on than a legal battle. Don't pick up one of Lescroart's books if you don't want to know about Glitsky's and Hardy's wives and ex-wives, their children, their fellow cops and lawyers and many other people, because Lescroart cares about them all. He also cares about San Francisco and describes its fogs and views and neighborhoods in loving detail. The Mercy Rule is 600 pages long, and it could have been half that if the author had wanted to deal only in courtroom drama -- but it wouldn't have been half as satisfying. It is perhaps worth noting that Lescroart is not a lawyer. He spent his twenties tending bar and singing in a rock band, which perhaps helps account for his focus on people as well as on the law.

Lescroart does not write "literary novels," but his books are highly literate as well as highly entertaining. The Mercy Rule is one of his best, but all six I've read have been first-rate. If I were starting to read him, I'd begin with the earlier books, to watch his characters unfold, but if you enjoy popular fiction, you can't go wrong with any of them. Most were recently reissued in paperback and are easily available.

Please join me in discussing this wonderful thriller online at www.washingtonpost.com/liveonline on Thursday, Nov. 21 at noon.