The National Park Service’s 2016 centennial got off to a rocky start.

On Jan. 2, militants occupied Oregon’s Malheur National Wildlife Refuge in a sustained attack on the very legality of public land—the philosophical and political foundation upon which the national parks and other reserves (including wildlife refuges) are built.

Then in mid-January came the galling announcement that one of the system’s flagships, Yosemite, is changing the names of well-loved landmarks in response to a legal dispute with a concessions company that managed to trademark park imagery and institutions for its own marketing purposes.

Neither is the sort of publicity that the agency hoped to receive from this anniversary, which was supposed to re-ignite the enthusiasm of the American public in a yearlong campaign called “Find Your Park.”

More in line with the message, surely, are two well-timed new books.

A Thinking Person’s Guide to America’s National Parks is an almost painfully earnest re-assessment of the national park system at the century mark. Its 23 chapters dissect the parks—why, and for whom, they exist. The book reflects the evolution of the agency’s approach to conservation, recreation, inclusiveness, sustainability and other facets. Between Ulysses S. Grant’s creation of Yellowstone National Park on March 1, 1872, and Barack Obama’s designation in February of three new national monuments comprising 1.8 million acres of California desert, the National Park Service has expanded its horizons generally from the West to the East, from scenic to historic, from wilderness toward urban areas. “The national parks are the American experience expressed in place,” writes former director Denis Galvin in the foreword, and as our understanding of the contours of that experience expands, the agency’s mission grows with it. “Today we contemplate the effects of a changing climate against the benchmarks of these protected places,” Galvin writes. “The story and contributions of enslaved people, once invisible, are now told.”

The book’s academic and in-agency contributors strike a measured balance between celebration and constructive criticism. The critiques mostly revolve around the agency’s slowness to come to terms with America’s history of oppression and diversity. These brief essays show an agency eager to attract young people and what we’ll soon enough need to stop calling minorities—the demographic core of whatever future support the parks may enjoy.

Population is increasing faster than park attendance, even as the system grows to meet its audience. The challenge is significant, and no book, however gorgeously illustrated (this one has 300 glossy color photos), is likely to be the magnet that draws new visitors into the parks.

But for anyone already invested, A Thinking Person’s Guide makes an excellent armchair roadmap to the Park Service’s more than 400 sites and its many priorities and pursuits, which range from community farming partnerships within the Ebey’s Landing National Historical Reserve on Whidbey Island, Wash., to the Kaibab Paiute Tribe’s leadership in preserving dark skies at Arizona’s Grand Canyon-Parashant National Monument. You might think of the book as an illustrated catalog of the nation’s grandest common holdings, and an eloquent (if indirect) defense of the principles and benefits of public land managed for public use.

The Wonder of It All, compiled by the nonprofit Yosemite Conservancy, takes a different approach, collecting 100 short anecdotes and testimonials to the parks’ transformative powers. They’re stories of first jobs, true love, encounters with bears and wolves and stars, and the sudden flare of a light in a child’s eyes.

The Wonder of It All demonstrates both the charms and flaws of anthologized amateur writing, but its stories exude a heartfelt passion that complements and sweetens the administrative efficiency of A Thinking Person’s Guide. Bob McConnell’s recollection of a night enjoying opera with veteran seasonal Yosemite ranger Carl Sharsmith, who died in 1994, offers an intimate portrait of one of the many indispensable volunteers who make the parks tick, while Rebecca Bailey learns that the less-than-flattering “green and gray” uniform is no deterrent to unsolicited male attention in “How to Talk to a ‘Girl Ranger.’” (“Respectfully” will do just fine, thank you.) Anybody who’s ever worn that iconic flat hat, or daydreamed of doing so, will likely enjoy these stories.

Both of these new books serve as invitations to the national parks—a reminder that it’s not enough to support the idea of the parks; we need to visit them in person and get to know them. As timeless and unassailable as they may seem, the parks are the tip of America’s public-lands iceberg, and if recent history shows anything, it’s that they require our constant protection.

Plenty of folks are fighting hard to find new ways to exploit our natural and scenic resources. For now, “We the People” have the stronger claim. We’d be remiss, and we’d be lessened, if we failed to exercise it.

The Wonder of It All: 100 Stories From the National Park Service

Edited by the Yosemite Conservancy

Yosemite Conservancy

320 pages, $18.95

A Thinking Person’s Guide to America’s National Parks

Edited by Robert Manning, Rolf Diamant, Nora Mitchell and David Harmon

George Braziller

300 pages, $24.95