Michael Chabon, the best writer of English prose in this country, and the most interesting novelist of his generation, is expressing amusement at the idea that anyone would think his new book might be anti-Semitic. Calling him an anti-Semite, Chabon says, would "be like calling Groucho Marx anti-moustache."

That's a pretty good crack until you remember that Groucho Marx painted on his moustache with bootblack.

Chabon's new novel is called The Yiddish Policemen's Union, and even those readers bowled over by the capacious inventiveness of his Pulitzer Prize-winning opus, The Amazing Adventures of Kavalier & Clay, are going to be amazed at how inventive Chabon can be. This mash-up of two pulpy genres--speculative science fiction and hardboiled detective story--is set in an alternate version of the present in which Israel did not survive the 1948 war of independence.

Instead, in Chabon's imagining, the post-Holocaust Jewish remnant was settled in Southeastern Alaska, about three hours north of Vancouver, where they have spent six decades building a teeming, crazy metropolis called Sitka, where Yiddish is the native tongue.

As the novel begins, this Jewish city of 3 million is about to revert to Alaskan sovereignty the way Hong Kong reverted to Chinese sovereignty. The Jewish experiment with self-rule is over. The Jews of Sitka are about to become a homeless, rootless, diasporic people again.