Theodore Roosevelt, who led the most famous volunteer unit in United States military history, was careful to point out that volunteer units are not in themselves a good thing, “the very best being, perhaps, up to the level of the regulars (as has recently been shown at Manila), while the very worst are no better than mobs, and the great bulk come in between.” Roosevelt’s Rough Riders were among the very best; the volunteers described in Rick Bass’s “The Diezmo” (Houghton Mifflin, 224 pages, $22) are no doubt among the very worst.

Military action is fresh ground for Mr. Bass, but he has long specialized in male passions. James Alexander is only a teenager when he joins an expedition commissioned by Sam Houston to patrol the southern border of the nation of Texas. “Volunteering” hardly describes Alexander’s experience of muster, and the first week of soldiering: “Each night we cleaned our weapons and sharpened our swords. The sound of the steel seemed like the sound of judgment itself, and we were overcome with wonder and relief at having been chosen. We would lead remarkable lives. We had been rescued.”

Roosevelt, writing 50 years after the events on which Bass’s novel is based, considered the Southwest an ideal breeding ground for good fighters, and Mr. Bass’s Texan boys have the same prejudice, and an even more intense faith in violent self-actualization. But where Roosevelt and his Ivy League companions maintained an interest in “the mysteries which lie behind courage, and fear” throughout their campaign, Mr. Bass leads his idealists into a pit of folly, and an atmosphere of sickening realism overtakes the action.

The hungry expedition first plunders the Texan town of Laredo, then crosses the border for little reason, only to take a priest hostage. Some of the men righteously desert, but Alexander cannot make up his mind to do so. Although he quickly realizes that his home was a prize he should have kept – “All that I now desired I had once possessed” – he sticks with the expedition, through capture, escape, and recapture.

Alexander survives by hanging back and working hard. After the existential moment of volunteering, he becomes passive. His best friend, James Shepherd, is a better joiner. After his arm is amputated, Shepherd is adopted by yellow-eyed Colonel Fisher, one of the expedition’s more ruthless leaders. Shepherd does become a warrior, following through on his dreams even as they are warped by circumstance. Alexander drops his dreams and preserves some boyish reticence, and survives intact.

“The Diezmo” is a departure for Mr. Bass. His second novel, it seems more effortless than much of his shorter work. Yet, strangely, the expedition’s misadventures are occasionally gross to the point of voluptuousness. At one point, on the run in the mountains, Alexander and his companions slaughter their horses with jeweled swords. Later they are imprisoned in a prison built into a mountain. Literary westerns, unless they are humorous, are almost inevitably precious. Rick Bass has sometimes walked this line, but in “The Diezmo,” Alexander stays on the side of sanity and good taste, mostly.

***

Alix Ohlin’s wild West is, like Alexander’s Texas, a place of troubled adolescence. “The Missing Person,” Ms. Ohlin’s impressive debut novel, is set in contemporary Albuquerque. Although some of her characters flatten under the pressure, Ms. Ohlin’s highly authentic plot is a rare success, a fresh take on the political contradictions of frustrated “heartland” youth.

Ms. Ohlin’s narrator, Lynn Fleming, is a listless graduate student living in Brooklyn. She is called home to look for her brother, Wylie, an “eco freak” who has disappeared into the mountains. Wylie is easily found, and in fact Lynn is drawn into his dreadlocked circle. Her new boyfriend, the mastermind of raids on swimming pools and over-irrigated golf courses, discovers in her a “secret rebellious side.”

But Lynn is closer to the truth when she determines that Wylie’s friends “seemed to do things – leave home, draw plumbing diagrams, move to Albuquerque, New Mexico – just to feel the sway of those passions on their bodies, for the sake of surrendering to them.” Although Ms. Ohlin never lets the hippies hold the reader’s sympathy, their idealism is enough to make us nervous of the grown-ups’ glib responsibility-talk.

“The Missing Person” is ultimately a study in priorities. Lynn negotiates between her mother and her brother, keeping her feminist academic career alive besides. These three value systems are genuinely incompatible, but all three are present, and Lynn treats them fairly, as Ms. Ohlin bluntly and justly forces her to do. Her plot’s flashpoints – Lynn has to point a gun at an eco freak to persuade him that a baby’s life is more important than activism – are too much like fireworks, but the basic premises of her novel are natural, up-to-date, and good.

***

Israeli author David Grossman cracks his characters open immediately, and writes their inner lives with swift, casual facility. The two novellas included in “Her Body Knows” (Farrar, Straus & Giroux, 272 pages, $25) are about forthright attempts to effect change in life.

The weaker of the two is the eponymous story, a concatenation of popular tropes. A woman reads a short story she has written to her dying mother. The story concerns the mother’s career as a yoga instructor, specifically an episode with a haunted 15-year-old boy her mother fell in love with. As the daughter reads, nervous but resolute, the mother interrupts, to complain about her pillows, or, eventually, marvel at her daughter’s skill. Her daughter would prefer to hash out lifelong misunderstandings. The intertextuality of daughter’s story and mother’s interjection is teasing, not least because of irritating alternating fonts, but the story is still extremely interesting.

“Frenzy,” the other novella, exploits the trick of intertextuality much more subtly. It describes a long car ride, between a brother and sister-in-law, in which streams of consciousness twist and couple. Over the course of the night’s drive, Shaul describes his wife’s possibly imaginary extramarital affair with such precision and emotional generosity that Esti’s faith in fidelity begins to vanish. She feels she has been standing on ceremony.

Effort shows everywhere in these two novellas, which are, after all, about art and imagination. “Frenzy” is excellent work, though long.