Marshall's first novel, A Separate Reality, was published in 2006 by Carrol & Graf and was nominated for a Lambda Literary Award for Debut Fiction.
The novel was well received and reviewed by The Washington Post, The Literary Review, The Orlando Sentinel, The Phoenix New Times, Bay Windows, the Lambda Book Report and by writers such as Robert Gluck (Jack the Modernist), Lynne Tillman (No Lease on Life), Christopher Bram (Gods and Monsters), and others.
Debra Liese, from the Literary Review, said "This quietly intelligent debut novel about one lonely, creative adolescent's search for identity amid the indignities of middle-school life is precisely what most literary novels I've read this year are not: as deeply sincere as it is ironic...Like Holden Caufield and adolescent narrators everywhere, Mark is painfully aware of falsity, but in Marshall's hands, this awareness is elevated to the level of a philosophical inquiry."
Wayne Koestenbaum, author of The Queen's Throat, said "A beautifully understated and evocative rendering of what it feels like to grow up as a 'misfit'...Robert Marshall's closeups of youthful sadness and elation, like Truffaut's or Bresson's or Solondz's, have a bitter, alienated clarity.
[19] In 2017, Marshall organized Writers Resist Trump, a large-scale lobbying effort and demonstration that accompanied the AWP (Association of Writers and Writing Programs) Conference in Washington D.C. Marshall told Publishers Weekly: "I looked and didn't see anything about people going to congress, and I thought that was a little weird."
In his review for Hyperallergic, Stephen Maine said "Commonplace yet unsettling, Robert Marshall's dreamlike images are derived from fleeting, fragmentary glimpses of the passing land- and cityscape, seen through the window of a moving car or train.