RUSSELL HOBAN'S most celebrated creation is a badger named Frances. Few American children make it through kindergarten without reading Bread and Jam for Frances, Bedtime for Frances, or Hoban's four other stories about literature's most appealing marsupial.

Hoban's newest book, about a 12-year-old boy named Riddley Walker, is filled with rhymes and stories that have all the unaffected charm and ring of the Frances stories:

Ful of the Moon Ful of the Moon

Ful of the Moon nor dont look back

Follereee Follerooo on your track

Oo hoo hoo Yoop yaroo

Folleree Folleroo follering you

If they catch you in the darga

Arga warga

But Riddley Walker is no children's story. From bread and jam and bedtime, Hoban has gone to create a remarkable novel about the most terrifying issue of the grownup world: the abuse of power.

From the first sentence, it is clear that Riddley Walker is not an ordinary story:

On my naming day when I come 12 I gone front spear and kilt a wyld boar he parbly ben the las wyld pig on the Bundel Downs any how there hadnt ben none for a long time befor him nor I aint looking to see none agen.

The entire novel is written in this language--mystifying but intelligible--and soon we learn why: the story takes place thousands of years in the future. The planet has been transformed, legend has it by a "flash of lite bigger nor the woal worl and it ternt the nite to day." The legend takes on an unsettling reality when we read that the "flash" was brought on by one "Littl Shynin Man the Addom."

The world that remains is dark, damp, and overgrown, peopled with primitive hunter-gatherers and horrible mutants. The language, too, has undergone a mutation: in Hoban's version of English reinvented from scratch, spelling, sentence-structure, and vocabulary have all taken on a childlike spontaniety and simplicity.

The resulting dialect has considerable appeal. Often, Hoban merges two words into one, with fascinating results. A woman is a "wooman," says Riddley, because "she's the 1 with the woom." The leader of the mutant survivors of the great flash is known as "the Ardship of Cambry," one who suffers many an "ardship." The most chilling pun has to do with the central myth of Riddley's time, an adaptation of the only document left from before the flash, the Christian legend of St. Eustace. In "the Eusa story," Eusa tampers with "the Littl Shyning Man" and creates the cataclysm. Eusa: remind you of any country in a pre-cataclysmic relationship with the atom?