Michael Chabon

Harper Collins, $26.95

What has Michael Chabon been up to for the past seven years? He's been writing; in 2002, he published Summerland, a lengthy baseball fantasy for young readers, and two years later, his novella The Final Solution imagined Sherlock Holmes as an old man. He's also created a series of comic books featuring the Escapist, the superhero he invented for his novel The Amazing Adventures of Kavalier & Clay, which won the Pulitzer Prize for fiction in 2001.

For a writer of Chabon's ambition, such projects seem ancillary at best. His 1995 novel Wonder Boys is, by turns, the funniest and bleakest novel about the writing life ever set to paper. Kavalier & Clay eclipses the line between literature and genre fiction, integrating elements of myth, history, pop culture and Jewish identity in a nearly seamless weave. What's exciting about these books is their sense that fiction can be provocative and graceful, challenging and flat-out, foot-stomping fun.

Chabon's new novel, The Yiddish Policemen's Union, is a spiritual descendant of Kavalier & Clay, a book that expands on the sensibility of the earlier novel and its roots in Jewish storytelling. It is a larger-than-life folk tale set in an alternate universe where issues of exile and belonging, of identity, nationality, freedom and destiny are examined through a funhouse mirror that renders them opaque and recognizable all at once.

The setup is a series of speculations: What if, as Franklin Roosevelt once suggested, a safe zone had been established in Alaska under U.S. protection for European Jews escaping Hitler? What if this Federal District of Sitka had grown and developed until its population was in the millions, a country within a country? What if Israel had collapsed in 1948, mere months after independence, leaving many Jews with nowhere else to turn?

And what if, 60 years later, Sitka was about to face a process called ''reversion,'' in which its territories would be returned and its Jews cast back into a Diaspora in which the desirability of their presence was not entirely assured?

The Yiddish Policemen's Union is the story of police detective Meyer Landsman and his attempt to unravel the execution-style killing of a junkie named Mendel Shpilman, found dead in his room in a Sitka SRO. Shpilman is the son of the Federal District's most powerful rabbi, a man who rules over his sect - known familiarly as ''black hats'' - like a crime boss, dispensing influence and favors, while remaining as aloof and enigmatic as a Talmudic text. For Meyer, a drinker who lives in the same hotel where Shpilman died, the case represents a last chance to redeem himself in his own eyes and those of his ex-wife, Bina, who is his supervisor.

What Chabon is setting up is a classic genre construction, murder as the tip of the iceberg, as the catalyst for an extended investigation into a way of life. Such an arc was perfected by Dashiell Hammett and Raymond Chandler. Chabon can't quite match their noirist chops, but he's got something else in mind. Indeed, for him, the alternate history, the murder mystery are less narrative devices than expressions of his desire to mix fact and fantasy, literature and popular entertainment, until we don't quite know where we stand anymore.

As we follow Meyer through his investigation, we get an education into an entire social structure in which policemen are called not cops but latkes. We see the latticework of underground tunnels that underlies the streets of Sitka, built by ex-partisans and survivors.

At such moments, The Yiddish Policemen's Union is at its finest, connecting fantasy to history and commenting on our elusive world. Some parallels are unmistakable - the Jewish-American Indian conflict standing in for that between Israelis and Arabs, the notion of the ''disputed areas'' as a North Country version of the occupied territories. Occasionally, Chabon draws these connections too bluntly. Yet these are minor quibbles in the face of the novel's fundamental sense of possibility, in which history and reality come together in an elaborate collage.