Charles Portis is one of my favorite authors. He's most famous for True Grit, which is a magnificent novel, but he's also written four other less well-known and appreciated novels. The most recent (published in 1991) is Gringos.
Gringos has a lot in common with Portis's other novels. Like True Grit and The Dog of the South, it's the story of an Arkansas native in exile. Like Norwood, the protagonist finds himself falling in with all kinds of colorful characters and a certain amount of danger he's not really prepared for. Like Masters of Atlantis, the esoteric and occult figure prominently.
The main character is an American living in the Yucatan, where he gives guided tours of the jungle and Mayan ruins and occasionally traffics in a little illicit Mayan antiquities. His life is upended by a couple of changes to his circumstances, including love (kind of ?) and the arrival of a band of dangerous hippies who may have something to do with a recent kidnapping in the United States.
To describe more of the plot would be both giving away too much and pointless. Because in any Portis novel the real joy is the narrative voice, the dialogue, the ramshackle collection of eccentric characters, and the preposterous set pieces that the plot meanders between. Also enlivening every one of his novels are marvelous little observations and asides like the two below, both from Gringos:
Simcoe read a book. It was all right to do that here. In the States it was acceptable to read newspapers and magazines in public, but not books, unless you wanted to be taken for a student or a bum or a lunatic or all three. Here you could read books in cafes without giving much offense, and even write them.
A passage that should make anyone who has ever read or written along in a restaurant grin.
Also, for a taste of the "Unsolved Mysteries"-like esoterica that drifts into Gringos:
Still, the flying saucer books were fun to read and there weren't nearly enough of them to suit me. I liked the belligerent ones best, that took no crap off the science establishment.
Do check out Portis's books; not just True Grit, which is a masterpiece and well worth your time, but his others as well. They're all great, and precious few.