DURANGO — Fifteen years after “The Western San Juan Mountains” introduced the geology, ecology and human history of half of the towering range that dominates Southwest Colorado, a companion tome is in bookstores.

Its title, appropriately, is “The Eastern San Juan Mountains.” Twenty-eight experts contributed to its 325 pages, which includes maps, tables, a glossary and an index. The book is published by the University Press of Colorado in conjunction with the San Juan Collaboratory, a joint effort of the Mountain Studies Institute, Fort Lewis College, the University of Colorado and the San Juan Public Lands Center.

Royalties from the sale of the book go to San Juan Mountains Undergraduate Fund at Fort Lewis College.

Laura Furney, managing editor of University Press, said the book about the western San Juans is in its fifth printing. She said a fifth printing is a milestone not often reached by University Press publications.

University Press, which was founded in 1965, has published an average of 25 books a year for the past decade, Furney said.

“That is a really solid number for us,” Furney said.

Rob Blair, professor emeritus of geosciences at Fort Lewis College, and George Bracksieck, former publisher and editor of Rock & Ice Magazine, edited the new book.

“I had it in the back of my mind to do a book on the eastern San Juans, but time goes by fast,” Blair said last week in explaining the long pause between volumes. “The first book planted the seeds for the Mountain Studies Institute, which became reality in 2002.

“I was involved in that effort, but I finally decided ‘I have to see if we can match the first volume,’ and I pulled together a team,” Blair said. “We probably started in 2005 or 2006.”

The eastern and western portions of the San Juan Mountains are divided, for the purpose of the books, by a north-south line that runs from Lake City to the point where U.S. Highway 160 crosses the Piedra River at Chimney Rock between Bayfield and Pagosa Springs.

Among easily recognizable names of contributors to the book are David Gonzales, professor and chairman of the geosciences department at FLC; Andrew Gulliford, professor of anthropology at FLC; Mike Japhet, a wildlife biologist retired from Colorado Parks and Wildlife; Koren Nydick, former executive director of the Mountain Studies Institute; Bill Ritter Jr., former governor of Colorado; and Duane Smith, professor of history at FLC and a columnist for The Durango Herald.

The first six chapters, which describe the geology, hydrology and temperature trends of the eastern San Juans, will require frequent trips to the glossary for readers not conversant with the topics. Chapters covering fens, fire, fungi and forest health, mountain lakes, wildlife, railroading and human history will be absorbed more readily.

“The chapters contain a lot of layered information,” Blair said. “More than one reading could be required.”

The ill-fated fourth expedition of John Fremont in the La Garita Mountains in 1848-49, described by Patricia Joy Richmond, a San Luis Valley historian from Dolores, and the history of railroading by Duane Smith, which necessarily revisits rail expansion in the western San Juans, recount interesting events in the Southwest in the second half of the 19th century.

A points-of-interest guide is the final chapter of the book. The authors describe what is visible at mile posts along a number of highways, including 85 miles of U.S. Highway 160 starting at its junction with U.S. Highway 550 in Durango.