The trooper circled the Cadillac. When he opened the passenger door, Atticus thought he was going after The Martian Chronicles, which was still up front somewhere. But the trooper came up holding The Safe Negro Travel Guide. He thumbed through it, at first puzzled and then astonished. "These addresses," he said. "These are all places that serve colored people?" Atticus nodded. "Well," said the trooper, "if that doesn't beat everything..." He squinted at the Guide edge-on. "Not very thick, is it?" Atticus didn't respond to that.

"All right," the trooper said finally. "I'm going to let you go. But I'm keeping this guidebook. Don't worry," he added, forestalling the objection that Atticus knew better than to make, "you won't need it anymore. You say you're going to Chicago? Well, between here and there, there's no place you want to stop. Understood?"

Atticus understood.

• Matt Ruff, Lovecraft Country (2016) 9

So in the original book, the guide is not a profession per se, it's a publication. Matt Ruff based the Safe Negro Travel Guide off of the real life The Negro Motorist Green Book which was publishd from 1936 to 1966. Several of these have been digitized and made available online so that you can get an idea of the contents. The series was profitable, as evidenced both by how long it lasted and how widely it was distributed.

The television adaptation of the book takes a few liberties with the plot, but it retains the basic idea that George (Atticus' uncle) is the publisher of the safe travel guide. So in that sense, yes it was a real profession.