Jefferson Turck is a lieutenant in the Pan-American navy in the year 2137. He gets his first assignment the Coldwater a combination submarine helicopter. He takes it out on a routine patrol from the Azores to Iceland. A violent storm damages the engines and forces to ship to cross the forbidden 30th meridian.
In this future the nations of the western hemisphere have come together to form one nation. The great war that started in 1914 had generated such an isolationist outlook the Pan-American Federation forbid any travel over 30 meridian in the Atlantic and 175 in the Pacific. Now two centuries later the rest of the world is an unknown terra incognita.
Turck decides to lead an expedition to explore Britain. While on this expedition he is left behind by a treacherous subordinate. Abandoned he sets out to find civilization. Britain is a desolate island that is overrun by lions and tigers that probably escaped from zoos. He rescues a young woman named Victory who turns out to be the queen of England. She had been deposed as queen and the two head over to the mainland.
Going down the Rhine the two are taken prisoner by black soldiers. Europe is now being colonized by the Abyssinian empire. Abyssinia now rules all of Africa and in a role reversal colonizes and enslaves the primitive tribes of Europe. Turck is sold as a slave to an Abyssinian general and Victory is destined for the emperors harem.
Taken to New Gondar a city built on the ruins of Berlin he arrives just in time to see the city fall to the invading Chinese empire. Rescuing Victory the two find the Chinese an advanced and civilized empire that rules all of Asia. Taken back to the capital Turck finds that the Pan-American Federation has established relations with the Chinese and he is considered a hero for crossing the meridian.
This book was written in 1915 and shows the strong isolationist sentiment at the time. I suppose for observers at the time it did look like the great war would drag on forever. The book also has the role reversal between Africa and Europe. This was a real interesting futuristic book. One of Burroughs more obscure but most unique stories.