Architecture, the subject of George Washington University professor (and sometime Essex County resident) Richard Longstreth’s wonderful book, is not the most prominent feature of the Adirondacks for most of us.

“The Adirondack region is best known for its incredible natural resources — millions of acres of wild and forested land, rugged mountains, miles of river and thousands of lakes and ponds,” notes Steven Engelhart, executive director of Adirondack Architectural Heritage in the book’s introduction. But Engelhart and his organization are committed to what he calls the “architectural treasures” of our area, and Dr. Longstreth’s exhaustive guide focuses on those treasures.

This is a very scholarly work, more than 400 pages long and filled with a bibliography, photographs, maps, short biographies of architects both living and dead, as well as descriptions and histories of Adirondack buildings. If that sounds heavy, academic and off-putting to you, the fault is mine, for “Guide to Architecture” is consistently accessible, interesting and well organized, and Dr. Longstreth writes clearly and simply.

In his 40-page introduction, Dr. Longstreth profiles and chronicles many different elements of the Adirondacks, including industry, recreation, transportation, conservation and heritage. By themselves, these pages are a careful summary worth the time of any reader who wants to learn about this area.

After the introduction, Dr. Longstreth writes first of fire towers and the Northway. About the Northway, built from 1960 to 1967, he writes, “No single project has had a greater impact on the [Adirondack] park, before or since.” Of course, he looks at this road with his architect’s eye, and offers a warning: “Overpasses and other components of the original infrastructure were generally simple and straightforward in design, complementing, but not competing with, the natural landscape. They are gradually being replaced by less visually sensitive structures.”

The bulk of the book, however, is an architectural exploration of 12 geographic areas of the Adirondacks. Each of these sections, such as “Great Sacandaga Lake” and “Ausable River Valley,” have their own introductions, summarizing that area’s history and reminding us of the variety within the area often imprecisely called the Adirondacks.

In each area, Professor Longstreth visits the towns, villages and hamlets (12 in the Ausable River Valley, e.g.) and profiles, often with photographs, the structures. The result is a book that teaches about what Longstreth calls “the built environment within the park.” For example, we learn the Keene Valley Public Library’s addition “is an admirable coupling of modernist design with a markedly older building.”

The guide, however, also satisfies personal curiosity. That house or public building we’ve driven by and wondered about? He answers our question. (For me, a building on the east side of Route 9N in Upper Jay? It was built in 1932, “the most architecturally impressive rural school in the Adirondacks.”) So it’s a book to read at home and take with you in the car.

In an email conversation, Richard Longstreth said that the book took him six years, “research, writing and production.” To get information about buildings, he sometimes knocked on doors. “I talked to a number of people, including some homeowners, about their properties when information was otherwise difficult to get.” He covered about 26,000 miles within the Blue Line researching this book.

In addition to the extensive bibliography, Dr. Longstreth mentioned the works of Barbara McMartin, Phil Terrie, Bryant Tolles and Craig Gilborn as especially important.

Professor Longstreth’s goal was to produce a “useful reference work — a concise history of the Adirondacks — as well as a field guide.”

He’s done that.