Lest Darkness Fall
by L Sprague de Camp (1939)

Classic alternative-history yarn about archaeologist Martin Padway who is catapulted back in time to the declining days of the Roman Empire. With the benefit of fourteen centuries hindsight, he becomes a Quaestor and sets about trying to the fend off the Dark Ages. Still manages to capture the imagination, especially for ancient history buffs.

Bring the Jubilee
by Ward Moore (1955)

In winning the War for Southern Independence, the Confederacy went on to become a strong and prosperous nation. Alternatively, the vanquished North misses out on the Industrial Revolution and sinks into poverty and despair. The protagonist time-travels to the Battle of Gettysburg. A big favourite for many years way down South in Dixie.

The Man in the High Castle
by Philip K Dick (1962)

The pick of the alternative-history bunch and the novel that established Dick as a major sci-fi writer. In 1962 the few surviving Jews live in fear and slavery is legal - all because America lost World War II. Sounds straightforward, but as usual it is not always clear who it is Dick has in his sights. As they say… what goes around, comes around.

Pavane
by Keith Roberts (1968)

British writer Keith Roberts gives alternative-history an Anglo twist in this fine set of interconnected short stories. This time it is the assassination of Queen Elizabeth I that changes the course of history. The 20th-century is dominated by a technophobic Catholic Church and the Inquisition is still up to its old tricks. Intelligent sci-fi fare.

The Anubis Gates
by Tim Powers (1983)

The AH formula gets a shakeup with this landmark steampunk novel from progenitor Tim Powers. A mild-mannered professor trips back to 1810 England where the colonisation of Egypt by Western powers triggers some bizarre encounters with sorcerers, werewolves, famous poets and other oddities. Stands up to repeated readings.

The Difference Engine
by Gibson & Sterling (1990)

Cyberpunk supremos steam it up in this tale of a computer-age that comes a century before its time. In a steampunk-typical Victorian setting, the authorities use primitive computers to keep punch-card databases on all citizens. A box of cards goes astray and dark secrets begin to unravel. Rich in detail, but a tad jargonistic in places.

Doomsday Book
by Connie Willis (1992)

The top sci-fi writer of the 90s turns in this eloquent tale of a mid-21st century history student who is mistakenly transported back to a medieval English village on the eve of Black Plague in 1348. Dark and sombre at times, the book is nevertheless a triumph of the human spirit. Popular in academic circles and generally regarded as Willis' best.

The Guns of the South
by Harry Turtledove (1992)

In 1864 Robert E Lee is convinced the Confederates are losing the American Civil War. A group of time-tripping white South African supremacists arrive bearing AK-47s as gifts and history is changed… for the time being at least. As always, Turtledove's historical nous is superb, clouded only by the occasional pedestrian narrative.