BOUNDARIES: What if Alaska, not Israel, had been the Jewish state?

Michael Chabon has boundary issues. A pop-culture junkie with a fantasy fan’s love of speculative fiction, he plugs comic books and pulp fiction into the spaces opened up by his historical “what if” questions and somehow molds it all into high art.

In The Amazing Adventures of Kavalier & Clay, these parts coalesced, with — among other transformations — the Jewish golem, legendary defender of the ghetto, morphing into a comic-book superhero. In The Yiddish Policemen’s Union, Chabon’s first full-length adult novel since that 2001 Pulitzer winner, he again revisits the repercussions of the Holocaust, grafting noir crime fiction onto a brave new world in which Israel never took hold. It’s an interesting mix, but after Kavalier & Clay, it’s also a bit of a disappointment, a rechurning of ideas into a thicker, less digestible brew.

Aside from the boundaries of style and genre, the real-space definitions Chabon considers here are of consequence. The action, which kicks off with a murder in a fleabag hotel, takes place in the Federal District of Sitka. Following the fall of the three-month-old state of Israel, this strip of Alaskan shoreline has been ceded as a temporary homeland for displaced Jews. (Chabon here is drawing on an actual failed proposal.) Sixty years later, as the book opens, the land is due to revert. In a few months, the exiles will once again be homeless. There are also the boundaries defined by eruv, the practice of marking off outside areas with string to make them symbolically part of one’s house, and thus exempt from certain laws of the Sabbath. Given that in Chabon’s world the strictest group of Orthodox Jews have also become its organized crimelords, such boundaries, as well as the concept of home and homeland, have weight. As the book’s oft-repeated refrain goes, “these are strange times to be a Jew.”

Enter Meyer Landsman, a divorced alcoholic detective who lives in the fleabag where the murder takes place. At once a character from classic noir and an embodiment of diaspora Judaism, he’s plagued by memory. Or as Chabon’s typically complicated, Yiddish-inflected introduction explains: “Landsman has been told, by the same loose confederacy of physicians, psychologists, and his former spouse, that alcohol will kill his gift for recollection, but so far, to his regret, this claim has proved false.”

He’s a sympathetic protagonist, this Landsman, mourning his marriage, his bush-pilot sister killed in a flying accident, and his own lack of commitment. Unprepared for the coming Reversion, he’s the only character not seeking a new home. His job should be his salvation; he places little faith in rumors of miracles and Messiah. But when his ex-wife, Bina, becomes his new boss and orders him off the case, even this hope dims. Like any classic gumshoe, he reacts by digging in, uncovering a meaty and believable conspiracy involving chess, Reversion, and those pesky rumors of redemption.

At times, Chabon’s chewy, Yiddish-speckled prose digresses into lengthy explanations of Orthodox customs or chess. And in the course of reconsidering the boundaries of the mystery genre, he occasionally falls prey to its common weaknesses. Because we have heard at length about the eruv, when string shows up as a clue, it can only be eruv string.

But these are quibbles. The elements here are more evenly balanced than in Chabon’s flat Sherlock Holmes pastiche novella, The Final Solution. Still, The Yiddish Policeman’s Union works best when it abandons the crime-fiction element to focus on its people. The crimes Chabon remains most interested in are those of history, the puzzles those of human nature.