Nightshift NYC, by Russell Leigh Sharman and Cheryl Harris Sharman, with photographs by Corey Hayes, University of California Press, $24.95.

Vandal Squad: Inside the New York City Transit Police Department 1984-2004, by Joseph Rivera, powerHouse Books/Miss Rosen Editions, $35.

To veterans of New York City life, an undercurrent of concern runs through the ongoing fiscal crisis, a worry that it could trigger disorder similar to what unfolded during the city’s last prolonged economic downturn. By the mid-1980s, New York had only just begun to emerge from a long decline (at least until the crack epidemic and another recession wreaked more havoc by the early 90s) in which neglect worsened conditions for impoverished neighborhoods, the homeless population surged and crime soared to record levels.

And while much in the city has changed in recent years – as illustrated by the calm reaction to the 2003 blackout compared to the mayhem that accompanied the 1977 power outage – the perception that the midnight hour morphs New York into a threatening metropolis still endures as conventional wisdom.

Not entirely without reason. In the so-called “city that never sleeps,” a 3:30 a.m. stroll in Times Square, even, reveals desolate sidewalks in a daunting landscape. Married co-authors Russell Leigh Sharman, a Brooklyn College anthropology professor who also published “The Tenants of East Harlem” in 2006, and writer Cheryl Harris Sharman spent one year plumbing the city’s overnights. They explain that when “…the day-dwellers lock themselves in against an accumulated fear of the night, the city slowly slouches into its own skin, revealing a vulnerability and an occasional mean streak to those who brave its darker side.”

Beginning in the spring of 2006, the Sharmans spent a year traveling throughout the five boroughs to explore the daily lives of individuals working long after most people have gone to sleep: 24-hour deli employees, cabdrivers, custodians and subway conductors. In other words, those who are usually invisible because they work in the shadows. What the authors unearth isn’t the frighteningly gritty landscape that has been seared into the public consciousness courtesy of Hollywood screenwriters since the 1970s. Instead, this nonfiction tour bypasses generalizations with thorough research and sharp reporting to illuminate a complex and insular world foreign to most New Yorkers. Over 18 chapters, each concerning a different theme in which the detail-oriented authors allow the story behind the rhythm of the night to unfold through the eyes of those who know it best, we learn that in the dark, New York actually has much in common with the rest of the country.

As the authors themselves point out, previous works like 1987’s “Night as Frontier” by sociologist Murray Melbin already have contrasted denizens of the night with their daytime counterparts. But with superbly non-intrusive storytelling, the Sharmans examine conditions faced by a labor pool of lower and working-class people of color – mostly immigrants from countries in South Asia, the Middle East, Latin America and the Caribbean – as they toil away on the city’s late shift in the age of globalization. With its focus on workers, as opposed to, say, nightclubs or crime, “Nightshift NYC” becomes a book about labor issues as much as anything.

Not surprisingly, an ample array of colorful characters materialize, but the strength of the book ultimately lies in its ability to connect those lives to the broader fault lines of society. And so, a Pakistani taxi driver, who resides in Brooklyn, tries to reconcile safety concerns with his own fear of picking up black pedestrians commuting to the borough. There’s the female registered nurse who, after working overnight at a local hospital, sacrifices hours of daytime sleep to maintain relationships with family members and friends. And a customs border protection officer at JFK International Airport who works the nightshift to put himself through college only to watch his grades plummet in the process.

From Penn Station to the Staten Island Ferry to the Fulton Fish Market (in its recent South Bronx incarnation) and beyond, the city provides fertile ground for compelling scenes to unfold in “Nightshift NYC,” complete with iconic black-and-white images by photographer Corey Hayes. Although the Sharmans were unable to secure as much cooperation from the NYPD as they would have liked – which surely constrains the view of the deadly gun violence that still haunts some neighborhoods – they still manage to document the tension-filled atmosphere ready to boil over in so many places. The toll of excessive alcohol consumption, for instance, becomes more tangible as the night wears on.

Despite the physical and emotional strain that often accompanies working the late shift, most of the Sharmans’ interviewees weren’t overly eager to escape it. At a time when the overall economic marketplace faces a level of gloom not seen in decades, this volume arrives with timely insight from those familiar with navigating through hours of darkness.

It’s been 25 years since the groundbreaking film “Wild Style” hit the silver screen and spread the rebellious world of hip-hop culture from its humble underground origins in New York to new audiences nationwide and across the world. Two of the era’s prominent graffiti artists, Fab Five Freddy and Lee Quinones, teamed up with director Charlie Ahearn to make a quasi-documentary on the vibrant and controversial art form that transformed the city’s subway trains into eye-opening and jaw-dropping wonders on rail.

For a generation of New Yorkers armed with spray paint cans, no scenario was more prized, from the 1970s through the 1990s, than the discovery of an understaffed rail yard station with idle trains ripe for “bombing” or “tagging” aliases, messages and assorted images. What some New Yorkers took to be a sad defacement of public property served as others’ brilliant canvases, with their promise of overnight celebrity.

As a bookend of sorts to the “golden era of graffiti” past, the reflections of a longtime Bronx resident and former police officer named Joseph Rivera at times meld the two views. Rivera recounts the time in 1987 when he noticed an immobile train behind a barbed-wire fence in Brooklyn – and his thoughts mirrored those of a typical graffiti practitioner. “It looked like a model just sitting there waiting for some action. When I first saw it I thought, ‘Boy, if I was a writer – !’” It’s a surprising admission given that Rivera was anything but a graffiti artist. In fact, it was his job to arrest as many taggers as he could find.

In “Vandal Squad: Inside The New York City Transit Police Department, 1984-2004,” Rivera chronicles his adventures on the front lines of the city’s campaign to combat graffiti. The result is a fast-paced and generally engaging work in which Rivera provides the rarely heard perspective of an enforcer, but a somewhat sympathetic one. While not the most introspective account, the tale is told with a swagger through vivid anecdotes that range from the humorous to the gut-wrenching.

By the early 1980s as assorted acts of subway vandalism hit peak levels, the Vandal Squad was created as an all-purpose anti-crime deterrent within the Transit Police Department. But as graffiti spread, the Vandal Squad was revamped to enforce an immediate crackdown. Rivera is generally effective in providing an outline of the history, but his breezy approach – primarily focused on the cat-and-mouse nature of the job – leaves some questions unanswered. One is left to wonder, for instance, about the Vandal Squad’s reaction to the intense public outcry surrounding the infamous 1983 death of graffiti artist Michael Stewart while in transit police custody, along with the subsequent trial and acquittal of six officers in the case.

Throughout the book, a fast-paced recollection of Rivera’s years in law enforcement that also profiles infamous taggers and their once-ubiquitous images, the author candidly writes about being “addicted to graffiti” while detailing his unit’s see-saw relationship with figures in the graffiti world during a turbulent era in the city’s history. At the conclusion of a useful glossary section, Rivera mentions: “Graffiti should be displayed in galleries and on canvasses, not on public property.” This prescription has the feeling of an afterthought, though – leaving the reader with the feeling that the author not only shares with his subjects (and targets) a common fascination with graffiti, but an interest in preserving some semblance of street credibility.

– Curtis Stephen