George Saunders  Texas-born, Chicago-raised, seven books, many prizes, satirist, Buddhist  is one of America's best short-story writers. But reading his new collection, Tenth of December, it seems like he's stuck. Saunders emerged fully formed with his 1996 debut, Civilwarland in Bad Decline. That book was met with whoops of joy: "scary, hilarious and unforgettable" announced Tobias Wolff; "wildly funny, pure, generous" applauded Garrison Keillor; "graceful, dark, authentic, and funny" cheered Thomas Pynchon (Thomas Pynchon!). A pre-Infinite Jest David Foster Wallace declared in an interview: "The person I'm highest on right now is George Saunders."

Since then, Saunders has remained faithful to the short-story form, painstakingly crafting new pieces, which land in the New Yorker or some other classy US magazine once every three or four months. His new collection is his first in six years. For those familiar with Saunders, it is undoubtedly more of a good thing. Trouble is, it's also more of the same.

Tenth of December presents 10 visions of America mostly filtered through the eyes of losers with one-syllable names such as Al and Kyle and Jeff. The stories tend to take place in self-contained suburban or small-town settings. No one here is successful or cool. Sometimes they are uncool in a virtuous way. Sometimes they are uncool and mean. The narrator of one story (his name is Ted) has the hesitant, disappointed voice of a typical Saunders protagonist: "Based on my experience of life, which I have not exactly hit out of the park, I tend to agree with that thing about, If it's not broke, don't fix it."

As usual with Saunders, the first thing you notice is the language, the exhilarating explosion of slang, neologisms, fake product names. The reader is wired into the protagonists' heads, the stories told either in the first person or in a third person that moulds itself around the characters' thoughts, taking on their voices. The first story, "Victory Lap", toggles between the perspective of Alison, a 14-year-old girl with delusions of grandeur ("The local boys possessed a certain je ne sais quoi, which, tell the truth, she was not très crazy about"); Kyle, a teenage dork in love with Alison ("In the dictionary under 'beauty' there should be a picture of her in that jean skirt"); and an unnamed murderer/rapist who attempts to abduct Alison ("If fuckwise it went good they'd pick up the freeway from there. Basically steal the van"). Few writers are so good at transcribing thought  Saunders never jams his own observations into his characters' mouths and he is especially skilful at mimicking the way fantasies and daydreams colour the way we think.

The distance between the characters' hopes and the reality of their situations is one of the themes Saunders returns to throughout Tenth of December. In "Al Roosten", for instance, the title character, a "round bald guy", boils with jealousy and self-loathing as he considers a richer, happier, better-looking acquaintance. Al is a masterful study of impotent rage, Dostoevsky's Underground Man transported to small-town America and stuffed into a gondolier outfit for a charity fundraising event.

Yet for all the successful stories, some of Tenth of December feels like it could have been lifted straight out of Saunders's previous collections. Set in a medieval-themed amusement park, "My Chivalric Fiasco" is a little too close to the caveman- and civil war-themed amusement parks seen in his earlier work. The fake product names in "Escape from Spiderhead" (MobiPak, ViviStif, Darkenfloxx) recall his other product names (I Can Speak, Aurabon® etc). And for a writer with such a great ear, it's a pity Saunders so often returns to characters with the same voice  the naive, slightly childish, slightly too literal guy who says things such as, "I knew Don Murray was her boss because Don Murray was also my boss" or "I could not help but wonder what tomorrow would bring".

If this collection does edge in a new direction, it is in Saunders's slight shuffle towards realism, away from the more wildly imaginative stories that dominated his earlier books (there is no sword-wielding packet of Doritos in this collection, for instance). One standout example is "Home", the story of a soldier's return from an unnamed war in the Middle East. Plot-wise there's nothing new here  Mike is suffering from something like post-traumatic stress disorder, the home he returns to is not the one he remembers, he feels alienated from everyone he meets. Yet the story unfolds in such an understated, unsentimental and funny way that by the end, it is impossibly moving. "Thank you for your service", becomes a bleak punchline, as everyone robotically delivers the same refrain to Mike.

Saunders has always balanced his satirical urges with genuine warmth and affection for his characters. And while critics often compare him to Mark Twain, Kurt Vonnegut and the master of deadpan absurdism, Donald Barthelme, an equally apt touchstone might be The Simpsons. Like Matt Groening's creation, the stories in Tenth of December mix crude and sophisticated satire of American life with an essentially warm-hearted, optimistic worldview. "Goodness is not only possible, it is our natural state," says Saunders in the book's acknowledgements. When his characters do bad things, it is usually because they are corrupted  by parents, by advertising, by pressure to get ahead, to be successful. Most of the time, though, they are just ordinary people doing the best they can.

David Wolf is books editor of Prospect

Since 1996, with the publication of his first collection CivilWarLand in Bad Decline, George Saunders's flamboyant satires of American life have become a major influence on a generation of younger short story writers, both in the US and internationally. His new collection, Tenth of December, is funny, poignant  in flashes, deeply moving  light as a feather, and consistently weird in the way that the suburbs are weird, which is to say quietly but intensely, under a surface as clean and bright as a newly waxed car.

Wherever a Saunders story is set, it's never too far away from the theme park. Previous collections feature characters whose work as reenactors (of the US civil war or prehistoric cave-dwelling) is absurdly arduous and meticulous, yet at the same time demeaning, poorly paid, and governed by strict, often absurd rules  in other words, much like most work. "My Chivalric Fiasco", one of Tenth of December's funniest stories, takes place in a theme park devoted to medieval court life, following a hapless minimum-wage reenactor who is given drugs that alter his brain to make him speak and feel more authentically "chivalric", with the result that, in the throes of knightly elevation, he spills the beans on his boss's rape of a co-worker, and is fired.

The suspicion that we are living in some kind of simulation, that our actions take place within a matrix of situations and behaviours that have been predefined, is a staple of postmodern fiction. Saunders points out that the experience of philosophical scepticism, which is usually presented as something important and exciting, perhaps involving CGI karate, is actually not unlike doing a crappy service-sector job. What is the point of "all this"? We are required to be "authentic", to speak and behave in character at all times. We are required to take a lot of things seriously (politics, finance) which feel tragic and ridiculous and utterly without meaning. If we step out of line, we're punished. Perhaps it's not even real  Saunders's fictions often present powerless characters trapped in a sort of chirpy, totalitarian Disneyland; in so doing they give a more acute sense of what it feels like to live and work in post-industrial, post-crash western economies than much journalism.

Saunders's characters are often outwardly perky, speaking the language of positive thinking and self-improvement; inside they are terrified, lonely, wracked by greed and guilt and passion. Small-town businessman Al Roosten is humiliated at a charity event, takes petty revenge for a perceived slight and entertains delusions of political grandeur, yet when it comes to real action he's impotent, unable to do more than exchange a "weak smile" with a passing vagrant.

Roosten, who could have wandered in from a John Updike story, exemplifies a more traditionally humanist strain in Saunders's fiction, a commitment which pulls him the opposite way to his postmodernist interests in consumerism, advertising and so on. It turns a collection of what might otherwise feel like a set of weightless conceits into something more engaged, making clear that Saunders, like all satirists, is also a moralist. In stories such as "Victory Lap", which deals with an attempted child abduction, and "Puppy", in which a mother taking her kids to buy a dog is confronted by the shocking sight of a disabled child chained to a tree, Saunders unearths in his landscape of bright double-garaged homes a vein of family trauma worthy of the darkest and most cluttered Viennese mansion. Authoritarian fathers, often offstage, dictate the behaviour of cowed and abject sons. Voices and consciousnesses frequently switch, so that "Victory Lap", for example, slides in and out of the minds of the abductor, the victim, and Kyle, a young neighbour who witnesses the crime. Knowing he should help, Kyle nevertheless has to struggle against the crushing weight of household rules and prohibitions instituted by his father, the "many directives, major and minor, he was right now violating". Kyle's sense of shame at his powerlessness is excruciating.

If the authority in some of these stories is often profoundly personal, it is also clearly the authority of the workplace, of social discipline more generally. In these stories, people are often cowed or bullied. They are required to carry out their assigned tasks, even at the cost of pain or personal suffering. They are required to give, not just their labour and their time, but some kind of emotional supplement  to smile, join in, have fun. It's as if the service sector has metastasised to colonise all of human experience. We're all working on our personal presentation, going the extra mile for the customer, no longer sure who or what the customer is.

Mood-altering drugs appear again in "Escape from Spiderhead", in which a convict, participating in a series of pharmaceutical tests, is given a substance that makes him feel passionate sexual love for a similarly drugged female inmate. From there things descend into a comical maelstrom of Milgram-esque psychiatric malpractice as Saunders burrows into questions about free will and the unsettling possibility that our desires could be manipulated, even chemically reconstructed. Instead of sovereign individuals, acting rationally in the global marketplace, we may be altogether more dispersed, controlled and abject.

 Hari Kunzru's latest novel is Gods Without Men (Penguin).