Unconditional romantic love can be a particularly subtle and damaging form of masochism. As the act of gamely rationalizing away flaws in the character of one’s beloved becomes a daily ritual, one’s misery and devotion increase by equal measure. The absolute best way to make the whole experience more excruciating is, of course, to get married.

Antonio Muñoz Molina’s sly and enigmatic new novel, “In Her Absence” (Other Press, 126 pages, $13.95), concerns a provincial Spanish bureaucrat named Mario López who has married, well out of his league, a beautiful woman for whom he could not be more poorly suited. Because Mario remains infatuated to the point of obsession with his wife, he must regularly engage in grueling mental gymnastics to a) convince himself that the marriage has any chance whatsoever of survival, b) not resent the relative tepidity of her feelings for him, and c) not break his mind as a result of the psychological contortions required for a) and b).

The reason Mario and his wife, Blanca, are not right for each other is that his frightful dullness (and he knows he’s dull; he tries to be otherwise but just cannot manage it) simply does not complement her petulance, frivolity, or persistent attraction to fashionable artistic poseurs. In Mr. Muñoz Molina’s frank, blunt sentences, one senses both pity and contempt for the ill-matched lovers.

Before Blanca, Mario’s life was drab. For seven years he dated a bland creature named Juli, but that quietly crumbled. (“How strange, he thought … I was on the verge of marrying a total stranger.”) There followed a time of watching videos alone and slowly, diligently reading Ramon Menéndez Pidal’s “History of Spain”: “He embarked on a plan to read it from the first volume to the last, and would always remember that he had made it to the obscure and tedious reign of the Visigoths when he met Blanca.”

Blanca is throwing up outside a nightclub when Mario meets her. Her breath, as he helps her home, is “an acid stench of alcohol, nicotine, and vomit,” and her apartment reeks of “old cigarette smoke and sheets long unchanged.”

But she is in possession of a bewitching body, which she offhandedly lets him glimpse “naked and white in the steam” as she showers with the bathroom door open. And so the staid bureaucrat tumbles into obsessive love with the foolish dilettante. At first it’s platonic, but she comes to depend on him — his reliability, his generosity, his willingness to clean her apartment for her — and soon they are married.

Blanca is from a wealthy family and can’t keep a job (“Another man might have thought she was flighty…”), while he is working-class and has been in the civil service for years, so it’s only natural that Mario should support them. He’s uxorious enough to sustain this state of affairs for a while, but inevitably Blanca grows disinterested in Mario, turned off by his constitutional indifference to art and “culture” (though he tries — so earnestly! — to fake it), and increasingly susceptible to the attentions of more worldly, decadent men — especially painters and “vile, conceited writers.”

Enter Lluís Onésimo, a pompous “multimedia” artist of questionable talent but, in Blanca’s eyes, much charisma. To Mario’s alarm, Onésimo gives Blanca a meaningless role in a show and she falls under his spell. She’s drifting away. Something happens — unclear what — and now Mario has finally lost her. He becomes distraught, nearly breaking down. Then, unexpectedly, Blanca returns to him with renewed affection, seemingly chastened by whatever’s transpired with Onésimo. But Mario, bizarrely, now becomes convinced that Blanca has been replaced with an identical imposter. Has the mental strain of his infatuation for Blanca turned him into a paranoid wreck?

Mr. Muñoz Molina’s writing is calculated and decisive, like a confident game of chess. It never thrills but it does have the capacity to illuminate and, to a degree, surprise. More importantly, it feels right for this material; the narrative of a marriage’s gradual deterioration is well served by the observant eye and deliberate pen Mr. Muñoz Molina applies to it. Its subtleties — the fractional decline of Blanca’s gratitude, the increasingly resentful tenor of Mario’s devotion — might have escaped a more bombastic stylist, but Mr. Muñoz Molina has constructed this short, precise novel as delicately as possible and the impression that lingers is one of chilly, cutting intelligence.

Mr. Antosca is a writer living in New York. His first novel, “Fires,” was published in 2006 by Impetus Press.