A Nomad of the Time Streams

In the first book, Warlord of the Air, Bastable finds himself transported to an alternate late-20th century Earth where the European powers did not stir each other into a World War and in which the mighty airships of a British Empire on which the sun never sets are threatened by the rise of new and terrible enemies. These enemies turn out to be the colonized peoples trying to break free, supported by anarchist and socialist Western saboteurs opposing their own imperialist societies, and led by a Chinese general whose country is still nominally under Western control and ravaged by civil war.

In The Land Leviathan, Bastable visits an alternate 1904 in which most of the Western world has been devastated around the turn of the 20th century by a short, yet terrible war fought with futuristic devices and in which also biological weapons were used. In this alternate world, an Afro-American "Black Attila" is conquering the remnants of the Western nations, destroyed by the wars. The only remaining stable surviving nations, aside from the African-based Ashanti Empire, are an isolationist Australasian-Japanese Federation, which opposes the Ashanti Empire, and the wealthy Marxist Republic of Bantustan, formerly known as South Africa which is led by its Indian-born president Mahatma Gandhi; having never known apartheid or hostilities between the British and the Boers, it is a wealthy, pacifist utopia, in which there is no racial tension.

In the final book, The Steel Tsar, Bastable witnesses an alternate 1941 where Great Britain and Germany became allies around the turn of the 20th century and thus neither the War of 1914 nor the October Revolution took place. In this world's Russian Empire, a much more stable and democratic nation than the real Russia has ever been, Bastable encounters a terrorist group which seeks to overthrow the Russian government and install a theocracy led by the religious fanatic Iosif Vissarionovich Dzhugashvili.