This is indeed a pretty mammoth collection of alternate histories. 20 stories, (3 of which are new to the collection), all of which are alternate histories. This is done in different ways - some are far into the future long after some diversion from our established history takes place, and some take place around what the author imagines to be a crux in history.
The quality is pretty high throughout (take a look at the list of authors to see that) and there was little in here that I personally disliked (though, of course you may not like as much as I did). In fact, even authors that I've never really fancied the idea of (Harry Turtledove, for one) have some enjoyable stories in this.
Given the number of stories, it's hard to provide comprehensive reviews of each (also, probably best to avoid spoilers!) suffice to say at the price, you can't really fault this. It's not perfect by any means, but there was little that I really hated, so give it a go!
James Morrow - THE RAFT OF THE TITANIC [New to the collection]: Everyone is evacuated from the Titanic in an audacious rescue attempt, but no-one is discovered. Set against the backdrop of what happened over the next few years. Good fun.
Ken MacLeod - SIDEWINDERS [New to the Collection]: Alternate history and the multiverse - features a chap that is able to jump between differing histories. Excellent stuff.
Eugene Byrne & Kim Newman - THE WANDERING CHRISTIAN: Christianity never quite gets the hold that it did. Basically a history of what happened over the preceding hundreds of years.
Suzette Hayden Elgin - HUSH MY MOUTH: Short story showing a different outcome from the American Civil war (and that doesn't mean a conventional "the south won" story). Good stuff.
Harry Harrison & Tom Shippey - A LETTER FROM THE POPE: Set around a crux point (explains it at the start too, handily) the idea here being that the Viking assaults on England in the 9th Century were never adequately repulsed, which would lead to the whole of England being subject to Viking rule.
Esther Friesner - SUCH A DEAL: The exploration of the new world doesn't go quite as we know it. In this version of history Columbus gets his backing from elsewhere. In this, we see Aztecs bought to Europe. Not my favourite, by any means, but a fun story.
A A Attanasio - INK FROM THE NEW MOON: This was interesting - written in a style which doesn't seek to make things easy for the reader. You have to work (a little) harder to work out the divergence here. Things we are familiar with are discussed in language and terms, which though not completely alien to us, are different enough to jar.
Pat Cadigan - DISPATCHES FROM THE REVOLUTION: What if Bob Dylan didn't come? This looks at what happens if the 1960s had turned out just a little differently through a series of journal entries and correspondence.
Fritz Leiber - CATCH THAT ZEPPELIN: In this, the German army is comprehensively defeated in the first world war. This leads to a better peace than the one we got - and some greater prosperity. Not least because Germany then is able to direct its energies in a far more productive way. It does sort of try to hide one of the reveals, but it's guessable... pretty good, though (if not my favourite here).
Paul McAuley - A VERY BRITISH HISTORY: The space race is accelerated and turns out a little differently! Good stuff.
Rudy Rucker - THE IMITATION GAME: About the persecution of Alan Turing (which really, of course, did happen) with some subtle twists. I enjoyed this one, I have to say.
Keith Roberts - WEINACHTSABEND: A "what if Germany won the war" story. Pretty decent this one.
Kim Stanley Robinson - THE LUCKY STRIKE: The Enola Gay crashes in an accident a few days before the bomb is due to be dropped on Japan. A different crew takes part, with future consequences. Considered a genre classic.
Marc Laidlaw - HIS POWDER'D WIG, THIS CROWN OF THORNES: The American Revolution fails, leading to a different now. Enjoyable.
Judith Tarr - RONCESVALLES: This one looks at a tipping point, where some small betrayals lead to different decisions concerning religion.
Ian R MacLeod - THE ENGLISH MUTINY: The Indian Empire becomes dominant and Britain is part of its empire. Looks to mirror some of the events that happened in our own imperial past.
Chris Roberson - O ONE: In an eastern empire, a man from the west is trying to sell his idea for a computational machine to the emperor. This puts him in competition with the chief computer, as mathematics on a large scale is labour-intensive and he wishes to protect his position. Pretty good, which surprised me as I haven't loved anything by Roberson that I've read until now.
Harry Turtledove - ISLANDS IN THE SEA: At another crux point. Telerikh, leader of the Bulgars, is choosing Islam or Christianity. Again, never really wanted to read any Turtledove, but quite enjoyed this one. It's obvious, though, what the choice will be!
George Zebrowski - LENIN IN ODESSA: Centred around Lenin, Stalin and Sidney O'Reilly (spy, on whom James Bond is supposedly based). Can't say too much without revealing what happens.
Pierre Gévart - THE EINSTEIN GUN: First translation from the French. The assassination of Emperor Franz Ferdinand fails, so the world isn't plunged into the first and second world wars. Some nice ironies with dates in this one.
Robert Silverberg - TALES FROM THE VENIA WOODS: The Roman Empire hangs on and prospers. An older man telling a story from his childhood about a n old man they met in the woods.
Gregory Benford - MANASSAS AGAIN: Hmmm...didn't really enjoy this one I have to day (and normally I quite like Benford). Has mechs in it though.
Pamela Sargent - THE SLEEPING SERPENT: Colonisation of the new world happens differently. Pretty good this one.
Frederik Pohl - WAITING FOR THE OLYMPIANS: Has a meta element to it (it's set around a man that writes "sci-roms" who needs a new idea, someone suggests an alternate history to it). In this, ancient empires survive and first contact happens...
Stephen Baxter - DARWIN ANATHEMA [New to the collection]: In the past, England becomes Catholic again. Darwin's ideas don't take on (he flees to the protestatnt Scotland). 200 years later, the inquisition digs up his bones for a trial. I enjoyed this (though I really do like Baxter).