In one sense, all fiction is alternate history. A Russian aristocrat named Anna Karenina in love with a Count Vronky never existed, so a universe in which she does exist is an alternate universe. But with its usual penchant for creating labels and carving up literature into subgenres, critics have decided that "alternate reality" refers only to fiction in which certain things have been changed and other things left alone. It's best if those things changed are very large.
By these criteria, Michael Chabon's novel The Yiddish Policemen's Union certainly qualifies. It starts small, with Meyer Landsman, a burnt-out case, almost a cariacture of noir: alcoholic, divorced, living in a flop hotel, a detective on the skids. A Jewish Sam Spade. Landsman is made aware of the murder of another sad case in his hotel, one Emanuel Lasker. From there the novel widens and widens until it includes a Sitka, Alaska, that has for 60 years been a provisional Jewish homeland; an Israel held firmly by Palestinians; Alaskan Indians tired of being screwed out of their land and willing to make strange alliances to reclaim it; a United States involved in a huge conspiracy to reshape the face of global politics; a Hasidic sect tired of waiting for this to happen by peaceful means; and a world that may have missed -- and misused -- its Messiah, who may or may not have been on either His first or second Coming. The scope of Chabon's vision is breath-taking, and so is his writing.
The novel is a Nebula nominee. Whether or not it wins -- and Chabon is not a member of our little club, so it may not -- go and read this book. It's terrific.