His most well-known work is the nonfiction book Beneath the Neon, which documents the homeless population living in the underground flood channels of the Las Vegas Valley.
His research about and interviews from inside the underground flood channels are detailed in his book Beneath the Neon: Life and Death in the Tunnels of Las Vegas, released in June 2007.
Nightline, The CBS Evening News with Katie Couric, Al Jazeera,[12] CNN, NPR, the BBC,[13] the Associated Press and other national and international media outlets have done stories about the tunnels and the tunnel-dwellers.
[25] In January 2016, O'Brien raised more than $13,000 in 24 hours through Crowdrise for his nonprofit Shine a Light to benefit homeless people living in tunnels beneath the Las Vegas Strip.
[28] In July 2017, O'Brien relocated to San Salvador in Central America to teach literature at an English-language preparatory school and to write a sequel to Beneath the Neon about the homeless people who made it out of the storm drains.
"[2] Central Recovery Press released the sequel, titled Dark Days, Bright Nights: Surviving the Las Vegas Storm Drains, in November 2020.
"[31] On November 17, on Dark Days, Bright Nights' release date, the Reno Gazette Journal published a related feature story profiling "Half Pint," one of the book’s interviewees, and detailed O’Brien’s background with the tunnels.
His fiction and poetry have appeared in books, journals, and exhibits, including Interim,[34] Winged Penny Review,[35] Twenty-two Twenty-eight,[36] The Argyle[37] and New Critique.
[38] As of March 2024, according to J David Osborne and Kris Saknussemm's Lost Xplorers podcast, Matt was working on a collection of short stories set on the streets of Vegas.
"[49] Midwest Book Review wrote, “With plenty of black-and-white photos, My Week at the Blue Angel is a fun and intriguing read that will prove very hard to put down.”[50] About Dark Days, Bright Nights, Kirkus Reviews wrote, “Powerful and relentlessly honest, the interviews explode myths surrounding homelessness while promoting compassionate views of the growing number of homeless Americans.