Tenth of December, By George Saunders. Bloomsbury, £14.99

"Goodness is not only possible, it is our natural state," says George Saunders in the acknowledgements to this unnerving, darkly witty collection of short stories. His low-rent characters are good people in a bad world, down on their luck, trapped in a discount store of moral choices. "What are we doing wrong here?" they ask, their small-town narratives underscored by a low boiling anger at more expensively gift-wrapped lives.

A war vet returns home to his trailer-trash single mother and her layabout lover to find everything messed up. His actions switch to semi-automatic and he starts "wrecking shit, see what happens". In another story, scientists create drugs which compress sensations of love and despair and give them trade-marked names like Vivistif and Darkenfloxx. They parody spontaneous, uncontrolled emotion.

In "Victory Lap", a suburban idyll is shattered by a young girl's abduction, a breakdown that releases unimaginable horror. A boy, witnessing the scene, suddenly snaps and beats the perpetrator's head to a pulp with a rock. "You did beautiful," says the girl's dad, as the kid, the Good Samaritan, becomes the murderer.

Saunders not only anatomises the hollow, morally ambiguous soul of provincial Americans, but celebrates their touching innocence. "You have to have joy. Joy kept a guy going," says an overweight character posing in his pants at a charity auction of "body-beautifuls". The skittish, playful monologues of the young are expertly pitched and very entertaining. A young boy in the title story, bullied at school, has created a complex universe in which he is the master warrior: "you are indeed a worthy adversary". The make-believe cosmos implodes when he encounters an old man contemplating suicide and, while trying to reach him, falls through the ice of a lake. The old man rescues the boy and, as both lives are in crisis, each gives the other a reason for living.

These are stories of integrity and authenticity, often wildly inventive. The raw nerve endings of these blue-collar tragedies are insulated by playfulness, humour and heart.