PERHAPS NO LITERARY FORM is more a creation of market forces and tradition than the short story. A novel can go on for as many pages as the author needs to finish the tale, and most book reviews clock in under 2,000 words, because, really, who needs more space than that to say whether a book is any good? The modern short story is short, however, because it fills a very specific niche: a tale that can be read in one sitting, first designed to fit the fiction slot in popular periodicals, and now repurposed for use in literary magazines and as a training exercise in creative writing classes.

If you need evidence of just how devilishly difficult it can be to work in this queer fish of a genre, look no further than Sam Lipsyte’s new story collection, The Fun Parts. Lipsyte, the Ritalin kid of contemporary American letters, likes to kick off his tales with an outlandish premise, stir in a few dollops of emotional intensity and gleefully demotic black humor, and let ’er rip. Thus, in one story, “Expressive,” he focuses on a wayward husband with a face so expressive he can make his inner thoughts readable to any woman he meets — including his wife, who throws him out of the house. In another, “The Dungeon Master,” the power dynamics of a medieval-themed role-playing game spill over into the teenage narrator’s daily world.

When he’s on, Lipsyte can sound like a latter-day Borscht Belt tummler rattling off jokes at the expense of precious yuppie parents, self-loathing teens, and junkies with hearts of gold. When he isn’t, as is the case all too often in this disappointing follow-up to his hilarious 2010 novel The Ask, his stories can feel like the literary equivalent of a hyperactive 10-year-old randomly tossing out fart jokes, off-putting punch lines, and retrograde observations of women, all in an effort to tame the thrumming motor of his distraction-addled brain.

The result is a story like “The Wisdom of the Doulas,” which opens, winningly, with a male doula — or “doulo,” as he prefers to be called — who doesn’t much care for babies or mothers. Mitch, Lipsyte’s narrator, notes that the word, now used to describe a labor coach who helps women during and shortly after the birth of a child, derives from the Greek term for female servant or slave. (“But don’t get any ideas,” he tells the new father in the story. “My rates are steep.”)

It’s a sly conceit, allowing Lipsyte to poke all manner of ill-tempered fun at type-A parents yearning for the idealism of their youth, and in the process, at the gauzy glow we superimpose over the messy, primitive process of birthing a child. “Picture a red onion with a mouth that isn’t even a mouth,” Mitch says of the infant in his charge, “but more some kind of incredibly loud air horn used by Satan to signal his peons to mop up all the infernal poop and gunk that spills forth from his fiery pan-gendered holes as he gives birth to every evil in the world.”

But despite this rich premise, or perhaps because of it, the story packs few real surprises. Mitch doesn’t care for his work, actively despises the family he’s been hired to help, and like nearly all of Lipsyte’s male narrators, he is a ticking time bomb of free-floating aggression. The couple he is assisting, a work-obsessed pharmaceutical company executive and his wife who name their newborn Prague because the...