What would possess someone to shoulder a pack and tromp about the backwoods for months at a time? No one has the definitive answer to that question, but taking to the open road and woods is a long-standing tradition in life and in literature. Hikers and even not-so-outdoorsy types fling themselves into these sorts of endeavors on a regular basis. The Sierra Mountains, the Appalachian Trail and ancient routes that served merchants and penitents — they all call to intrepid travelers.

PHOTOS TO INSPIRE: 9 epic long-distance trails

Such locations also attract writers, and a slew of great books have emerged in recent decades on the mindset and the restlessness of the long-distance traveler. The desire to explore and recount these tales goes back eons, but the modern era has been productive for wanderers determined to put pen to paper.

A few titles become bestsellers, and others deserve to be considered trail classics, but they are all worth a read.

The cover for 'The Dharma Bums' by Jack Kerouac1. "The Dharma Bums" by Jack Kerouac

Jack Kerouac, Beatnik icon and part-time ranger, penned the mid-20th century classic "On The Road" to great fanfare. His follow-up novel is the lesser-known but equally profound "The Dharma Bums." In it, Kerouac explores the lure of the wilderness and the appeal of city life.

Kerouac draws upon his wandering lifestyle to create the character Ray Smith. Through Smith, he urges readers to resist the pressure to conform to cultural norms, envisioning a millions-strong tribe of wanderers that renounce consumerism in favor of experience. He calls it the "rucksack revolution," a manifesto for a generation of would-be counterculture types who'd rather climb, ski and surf than pursue careers.

The midsection is a tribute to a riotous journey into the Sierra Mountains that takes readers to dizzying heights on a boulder-strewn, bone-jarring ascent up 12,000-foot Mount Matterhorn. Along for the climb is a fictionalized version of the Zen poet Gary Snyder. Perhaps best of all are the climbers' observations of the living in the moment that are written in passages as refreshing as a clear mountain stream on a hot summer day.

The cover for 'A Walk in the Woods: Rediscovering America on the Appalachian Trail' by Bill Bryson2. "A Walk in the Woods: Rediscovering America on the Appalachian Trail" by Bill Bryson

Published in 1998, "A Walk In the Woods" recounts Bill Bryson's ill-fated attempt to hike the Appalachian Trail and offers an amusing glimpse at the subculture of long-distance hikers. Known to devotees as the AT, the Appalachian Trial attracts tens of thousands of hikers each summer who head to its many trailheads dotting the Eastern Seaboard. The granddaddy of hiking trails in the U.S., the wilderness path spans 2,100 miles from the wilds of Georgia to Mount Katahdin in Maine. A hardy subset of hikers attempts to traverse the entire length of the AT each year. In springtime, hikers begin the start of a long, rugged slog across 14 states in the hope of reaching their destination by the onset of winter. Imagine running a marathon every other day for about six months.

Early on in "A Walk in the Woods," readers realize Bryson has underestimated the physical and mental demands that the AT places on long-distance hikers and what it means to wake up tired and hungry each day. Hikers endure the process over and over again until exhaustion takes its toll or resignation sets in.

Despite the hardships, Bryson is laugh-out-loud funny as he lurches from one campsite to the next, attempting to make meager headway. Tempers flare and gear gets thrashed. Bryson relies on his trademark wit to bear witness to his ineptitude and the foibles of his fellow trail mates. With foul weather, bugs and the lack of food, Bryson delivers a hilarious account of life in the backcountry. The book encapsulates why so many people feel compelled to hike the AT, but also why few succeed.

The cover to 'Wild: Lost to Found on the Pacific Crest Trail' by Cheryl Strayed3. "Wild: Lost to Found on the Pacific Crest Trail" by Cheryl Strayed

Competent hikers well-versed in the vagaries of trail life take uneventful trips and write how-to books. In "Wild," Cheryl Strayed demonstrates none of these qualities. In fact, she's a danger to herself at the onset of the book. Recently divorced, grief-stricken and in danger of becoming addicted to heroin, Strayed needs to step outside of herself. And the trail beckons.

The book opens the sacrifice with of her ill-fitting boots to the trail gods, which demand blood, sweat and tears. At 26, Strayed decided to hike the Pacific Crest Trail (PCT) on a whim. Based on information gleaned from guidebooks, her next move was to embark on a 1,100-mile journey from the Mojave Desert to the Columbia Gorge in Oregon.

Burdened with a heavy mental and physical load, Strayed threads her way through the wilderness almost in complete isolation. For her, the PCT is both a balm and a curse since there's not much room for doubt or self-pity as the mountains begin to close in around her. The trail offers few choices except to put one foot in front other — and to marvel or to curse at the scenery. Nothing calamitous happens, but she's not unscarred by the experience, either. In the process, she learns valuable lessons about survival and self-acceptance, in a memoir that's as much a guidebook to life as a wilderness narrative.

The cover for Off the Road: A Modern-Day Walk Down the Pilgrim's Route into Spain' by Jack Hitt4. "Off the Road: A Modern-Day Walk Down the Pilgrim's Route into Spain" by Jack Hitt

"Off the Road" is less a how-to book than a why book. At age 35 and in a bit of a funk, author Jack Hitt sets out to hike the Way of St. James. The route known, as "El Camino," is a series of footpaths punctuated by market towns and gorgeous scenery through France and Spain. The 500-mile long path leads to the ancient capitol Santiago de Compostela, a UNESCO designated World Heritage Site.

In it, he walks through an ancient landscape while braving the elements and the discomfort of blisters and backache. A mix of travelogue and history book, Hitt maps out the origins of El Camino and why it endures as one of the most significant pilgrimage routes of Christendom. An agnostic, Hitt questions the value of faith in the modern world. But by journey's end, he can't help but admire the willpower of the millions of people who came before him, and the faith-based wayfarers who now share the route with hikers and fitness buffs on their own quest to complete the journey.