Ian Watson & Ian Whates, eds. The Mammoth Book of Alternate Histories (2010).
In one of his earliest takes on defining SF, Samuel R. Delany suggested different kinds of ‘subjunctivity’ for realism, fantasy, & SF, the latter defined as ‘events that have not happened.’ This allowed for alternate history, which is ‘Events that have not happened in the past.’ I happen to really enjoy good alternate history, & the editors of The Mammoth Book of Alternate Histories have collected a bunch of the best short tales in this sub-genre, including 3 written just for this anthology.
There isn’t a bad one in the bunch, but some are especially well done. All 3 new stories work well. James Morrow’s ‘The Raft of the Titanic’ proposes a new politics among those who survived that disaster although the world did not know. Ken MacLeod’s ‘Sidewinders’ is a fine version of a war between 2 different time armies trying to construct their version of history, while Stephen Baxter’s ‘Darwin, Anathema’ shows us a 2009 world controlled by the Catholic Church, where science is very different from our history. Among the many reprints, Fritz Leiber’s ‘Catch That Zeppelin,’ Keith Roberts’s ‘Weinachtsabend,’ Kim Stanley Robinson’s ‘The Lucky Strike,’ Chris Roberson’s ‘O One,’ Robert Silverberg’s ‘Tales from the Venia Woods,’ Pamela Sargent’s ‘The Sleeping Serpent,’ & Frederik Pohl’s ‘Waiting for the Olympians’ (with its tip of the hat to Cafavy’s ‘Waiting for the Barbarians’) stood out for me.
So my favorites are mostly different outcomes of World War II or much earlier changes that utterly alter the 20th century. Some of the best alternate histories are novels, where the writer can work out many of the speculative possibilities. The best short fiction in this sub-genre finds a way to suggest huge changes through some small specific details. The stories in The Mammoth Book of Alternate Histories do that very well, indeed.