Alternate history continues to fascinate the science fiction world. One of the UK's leading SF authors, Stephen Baxter, made much of his reputation through alternate history, particularly stories of space exploration programmes that never quite were (e.g. his award winning 1996 novel Voyage). Many other authors have at least one alternate history story to their credit. And the genre also appeals to non-genre authors; examples are Robert Harris's 1992 novel Fatherland and Philip Roth's The Plot Against America (2004). Foundation, Vector, and the fanzine Journey Planet have all devoted recent editions to the topic.

The appeal is partly the attraction of the costume party, of seeing the familiar in unfamiliar garb. But it's also that of the opportunity to examine the assumptions by which we exist, to imagine what might have happened had we or our forebears, as nation or race, acted differently. Some historians remain sceptical of the concept, but others have embraced it under the term "counterfactual", as collections edited by prominent scholars such as Niall Ferguson (Virtual History, 1997) and Andrew Roberts (What Might Have Been, 2004) show. As a trained historian myself, I would say that the job of the historian is to think through what might have happened had different decisions been made, the better to understand the decisions that were made.

So it's not surprising that the Mammoth series of entry level anthologies should get round to alternate history. This volume has been put together by one of the leading editors and publishers of UK short fiction anthologies, Ian Whates, and his regular collaborator on various projects, noted SF author Ian Watson—it is, in some ways, a Newcon Press volume in all but name. In it are found twenty-five stories of alternate history, three new, one published in English for the first time ("The Einstein Gun", by Pierre Gévart), and twenty-one which have appeared before.

Of the three new stories, James Morrow's "The Raft of the Titanic" is well-written, but has a fairly silly premise, which becomes sillier as the story develops. It is presumably intended as satire; there are points where Morrow is clearly inviting you to laugh, at least if you know anything about the Titanic. But in the end it appears as if Morrow is treating this whole story as an amusing divertissement, with no intent to do anything more serious.

Stephen Baxter produces "Darwin Anathema", inspired by 2009's Darwin bicentenary. The story is perfectly fine, if not perhaps Baxter at his best. I'm not sure I'm as confident as Baxter seems to be that good old-fashioned British compromise would survive the introduction of the Inquisition to the UK's shores.

Best of the new stories is Ken MacLeod's "Sidewinders". The premise here is that every time someone can’t find their keys where they thought they left them, they have in fact slipped into an alternate universe where they left their keys somewhere else. I found myself thinking of Graham Dunstan Martin's novel Time Slip (1986), where people about to die slipped into a parallel world where they were not going to die. MacLeod's "Sidewinders" are people who are aware of their ability to cross the divide, and can leap to a universe where there's a more significant change that simply a new location for someone's keys.

The reprint stories are taken from various sources. Some, such as Kim Stanley Robinson's "The Lucky Strike" or Robert Silverberg's "Tales from the Venia Woods", are acknowledged, and sometimes award winning, classics of the genre. Many of them have been anthologized in earlier alternate history volumes, either as first publication, or subsequently collected—three stories, Robinson's, Fritz Leiber's "Catch that Zeppelin!", and Pamela Sargent's "The Sleeping Serpent", were all collected in Martin H. Greenberg's 1996-edited volume The Way It Wasn't: Great Science Fiction Stories of Alternate History. It looks as if Watson and Whates's first act was to go to other collections and see what they contained. Some might consider this laziness, but it's really just starting one's research in the right place.

For it would be unfair to deny that considerable thought has been put into this anthology. It is easy to characterize alternate history stories as being solely interested in alternate Hitlers, Zeppelins, steam-driven cars and a victorious Confederacy. The cover of The Mammoth Book of Alternate Histories might suggest that this volume had bought into those clichés, since it does feature both Adolf Hitler and a Zeppelin. In fairness, this cover does illustrate one of the stories included, Leiber's. Moreover, "Catch that Zeppelin!" is the only story to feature Zeppelins, and one of only three with an alternate Hitler, and in one of these, "The Einstein Gun", Hitler is given a single throwaway mention. Only one story, Keith Roberts's "Weinachtsabend", truly fits into what the Encyclopedia of Science Fiction calls the "Hitler Wins" genre. There is also only one story in which the Confederacy wins the American Civil War, and even that has a slightly unusual take (Suzette Haden Elgin's "Hush My Mouth"; there is also Gregory Benford's "Manassas, Again", with a very different version of the Civil War, that does not involve the Union and Confederacy at all). And steam powered cars are wholly absent.

Instead, this collection showcases a wide diversity of alternate settings, diverging to lesser or greater extents from history as we know it, from Robinson's slightly different version of the end of the Second World War, to Silverberg's Europe in which the Roman empire never fell. If one can detect any trend in the selection, it is a slight tendency towards stories that overturn the European Christian domination of the planet. In Harry Harrison and Tom Shippey's "A Letter from the Pope" (co-written by an academic, thus perhaps with sounder historical credentials than some) Alfred of Wessex wavers between Christianity and paganism. Judith Tarr's "Roncesvalles" and Harry Turtledove's "Islands in the Sea" have Islam on the brink of overwhelming Europe. A. A. Attanasio's "Ink from the New Moon" and Chris Roberson's "O One" show worlds dominated by China, whilst in Sargent's, the Mongols conquered Europe. Reversals are found: in Esther Friesner's "Such a Deal", Aztecs return with Columbus and overthrow the Spanish monarchy, whilst in Ian R. MacLeod's "The English Mutiny", India rules Britain rather than the other way round. A number of stories depend on the Roman empire not falling in the west in the fifth century CE—Ken MacLeod's, Silverberg's, Benford's, and the longest story in the collection, Frederick Pohl's "Waiting for the Olympians" (the shortest is Haden Elgin's).

Another cliché confounded is one expressed by Brian Stableford in the episode concerned with parallel universes of the BBC's television documentary series The Martians and Us—that the alternate history portrayed is always worse than that which is ours. True, Baxter's Inquisition-run twenty-first century is not an attractive society. Nor has Haden Elgin's post-Civil War collapse of both North and South created any prosperity. On the other hand, Leiber's 1930s seem much more settled than our reality's, and the British-dominated space race of Paul McAuley's "A Very British History" is an attractive world that should stir the heart of any fan of the comic series Dan Dare. Other scenarios, such as Attanasio's, Roberson's or Ian MacLeod's, are more neutral, and are only likely to upset people ideologically committed to Europeans' manifest destiny to rule the world, either directly or through their colonies. Taking this a step further, the message of Gévart's story is that, however bad one thinks one's own existence, the alternatives could be far worse.

Intellectually most intriguing of the stories is George Zebrowski's "Lenin in Odessa". Here, the Marxist notion of historical inevitability is critiqued though the lens of alternate history. Since Stalin still ends up in charge of the Soviet Union, it is not clear how much historical inevitability has been thwarted—but the story is in any case as much about Stalin's misuse of that notion to cloak a belief in his own personal manifest destiny.

The collection also demonstrates diversity of approach. Most entries here are in traditional story form, but others take the documentary format more popular amongst the counterfactuals of historians. McAuley's story is a review of a fictional non-fiction book, whilst Pat Cadigan's "Dispatches from the Revolution" collects a dossier of eye-witness accounts recording events that pitch the United States into totalitarianism. Some stories, such as Robinson's or Morrow's, show the point of divergence (the "Jonbar" point, as SF critical jargon has it). Others. such as Silverberg's or Marc Laidlaw's "His Powder'd Wig, His Crowne of Thorns", show the world centuries after things have changed. Whilst most of the stories are what I would call "pure" alternate histories, that is stories set in a world where history has run along different lines, with no further SF elements, there are also stories here that are SF stories set in alternate worlds, such as Pohl's (whilst Eugene Byrne and Kim Newman's "The Wandering Christian" is alternate-world fantasy). In some the concept of the alternate world is important to the plot, such as in Ken MacLeod's, Leiber's or Gévart's. Rudy Rucker's "The Imitation Game", whilst science fiction, could be argued to be not alternate history at all, since nothing in it is incompatible with what we know of the historical period concerned.

Given all this recognition of diversity, and in light of the recent controversy over The Mammoth Book of Mindblowing Science Fiction's selection of exclusively white male authors, it is a shame that only white male authors are listed on the cover of this collection. I appreciate that Watson and Whates want to highlight the authors of the new stories, and then what are perceived as famous names. And there are women writers amongst the selection inside (Cadigan, Tarr, Haden Elgin, Friesner, Sargent). I just feel it is a pity that room could not be found on front or back covers for one of these women.

If I were to criticize the selection of stories, I would probably highlight the bias towards the last twenty-five years. The oldest story is Roberts's, from 1972, and there is only one other story from the 1970s (Leiber's, from 1975). All the other stories date to after 1984. Part of this may be the result of taking a number of stories that were originally commissioned for Benford and Greenberg’s 1990 anthology What Might Have Been, Volume 2, which featured the stories by Harrison and Shippey, Laidlaw, Tarr, and Zebrowski. Alternate history stories have been going for much longer than this. Leiber began his Changewar series in 1958 ("Catch that Zeppelin!" is from that series, but works perfectly well in isolation). And there is, of course, L. Sprague de Camp's "Lest Darkness Fall", from 1939.

Beyond that, there are absences to be noted. Silverberg and Turtledove are represented, as one would expect, and "The Lucky Strike" is here. But you will not find in this volume Bruce Sterling and Lewis Shiner's 1986 cyberpunk classic "Mozart in Mirrorshades", or indeed anything else by Bruce Sterling, who has been a key writer of alternate history over the last three decades. Though "Weinachtsabend" is a prize-winning story, one might have expected Keith Roberts to be represented by one of the Pavane stories of a Catholic and technologically backward England, which have perhaps been more influential on the genre. A major author in exploring the concept of alternate universes has been Michael Moorcock, though I’m not sure he has written anything in the short story format quite suitable for this volume.

But second-guessing the selection is slightly unfair. One cannot know which stories the editors would have liked to have, but were unable to obtain. Watson and Whates have set out to provide an introduction to alternate history. The omissions mean that this cannot be considered the definitive collection of alternate history stories (as if such a thing were possible in the first place). But they have certainly provided an introduction to the subject, one that successfully showcases the variety of what alternate history can do. I would happily recommend this work to anyone on that basis.

Tony Keen trained as a student in Ancient History. In an alternate history, he is a professor at some provincial university, but gave up writing about science fiction long ago.