It's fortunate that Tony Hillerman chose to focus his considerable storytelling skills on the unlikely and lonely area of the Navajo and Hopi reservations of Utah, Arizona and New Mexico. Otherwise, millions of Americans would never have peered into a culture that is both the same and different from their own.

Hillerman, of course, writes primarily mystery novels, but they are more than that. He created the fictional Navajo police officers who have won a devoted following, and he brought the Navajo and Hopi cultures into our living rooms. (Or airline seats - you see a lot of his books in airports.)This latest book currently ranks eighth on the New York Times best seller list, but we knew it would be at least that high as soon as it came out. It is his 12th book to chronicle the fortunes of the sagacious Joe Leaphorn and the impulsive Jim Chee, Navajo policemen who seem to have the same kinds of problems and frustrations as everyone else.

In "The First Eagle," Joe Leaphorn has recently retired from the force but is pressed into doing a private investigation to find a missing biologist. Jim Chee, his sometimes resentful understudy, is an acting lieutenant, wrestling with administrative obligations and police work in a part of the country where help can be hours away.

The story centers around a group of scientists, including doctors and biologists, who track the viruses that plague the Southwest. That includes a particularly virulent form of bubonic plague. Their research involves tracing the link between infected animals and humans. When one of them disappears, and at the same time a Navajo policeman is murdered, the stories begin their intricate interplay.

As always, Hillerman writes in a straight-forward prose that simply assumes the Navajo culture as a given, while making it a necessary backdrop to a story that could be set in another place or time. He thinks we will be captivated by it, and he's right.

A great example occurs when Lt. Chee sets out to capture a live eagle - and a specific one at that. The matter-of-fact account of how he does this, operating patiently from a lonely blind, high above the valley, makes you almost feel the dust and heat of the surrounding desert.

Hillerman treats all of this with great respect - except the FBI, whose agents do not fare well as they try to work within the Navajo culture. It's always a pleasure to see how the Navajo officers are underestimated - another undercurrent in many of Hillerman's books.

Hillerman's fans won't be disappointed. He does tilt toward repetition in this book, however, as various characters explain again just what they are doing as biologists, or as Leaphorn says for the fourth time that he doesn't believe in coincidences. Those are niggling criticisms, however, for a well-written yarn that will get you through a long airplane journey.

(Addendum. Hillerman notes that since he began his fictional relationship with the Navajo Tribal Police, six of its officers have been killed while performing their duty. He dedicates the book to them: Burton Begay, killed in 1975; Loren Whitehat, 1979; Andy Begay, 1987; Roy Lee Stanley, 1987; Hoskie Gene Jr., 1995; and Samuel Redhouse, 1996. It's a sobering reminder that their work is not only lonely, but also dangerous.)