The four books in the series, Mortal Engines (2001), Predator's Gold (2003), Infernal Devices (2005), and A Darkling Plain (2006), focus on a hypothetical future taking place thousands of years after a deadly war between Greater China and the American Empire where the majority of settlements have converted themselves into traction cities and where technology from before the conflict is known as Old Tech and is significantly more advanced than anything that emerged afterwards.
Sometimes referred to within the Mortal Engines community as the "original quartet", the Mortal Engines Quartet is the core of a larger franchise, which includes a prequel trilogy, the Fever Crumb series; several short stories, two spin-off books, The Traction Codex and The Illustrated World of Mortal Engines; and a film adapted from the first book.
Philip Reeve has stated that he originally thought of the idea of traction cities when people where complaining about the growth of a city that threatened to engulf smaller towns. Before the first book was written, Philip Reeve wrote the short story Urbivore. It has several similarities and differences to the eventual settings of the story. The characters where originally going to be adults, but he later changed them to teenagers. As Philip Reeve was an illustrator when he was writing Mortal Engines, it took over six years to write between different jobs.
- Main article: Timeline
The Quartet is set in the far distant future, in an age known as the Traction Era. Earth has been reduced to wasteland by a devastating conflict, known as the Sixty Minute War. Nations no longer exist, except in the lands of the Anti-Traction League; Traction Cities - entire cities mounted on caterpillar tracks for mobility - are fiercely independent city-states, using giant jaws to devour one another for resources. Trade is mostly accomplished by airship, though sometimes cities of roughly equal size (unable to devour each other) will stop to trade. Old Tech is the most sought-after commodity.
World of Mortal Engines
- The Great Hunting Ground - Consists of Europe and Northern Asia, and is the domain of the Traction Cities. It is a muddy wasteland, as the constant movement of the cities has destroyed all vegetation. The land is referred to by city-dwellers as the "Out-Country". As it is called the Great Hunting Ground it is likely to be the biggest in the world, with the most traction cities.
- The Ice Wastes - New name for the Arctic, which is also home to Traction Cities which use iron runners to skate across the ice. In some places the ice is thin and a danger to traction cities as they risk falling in the ocean.
- Africa - Africa is split between the Sahara Desert, which is a land of Traction Cities, and the southern regions, run by Anti-Tractionists. Areas of the southern continent include the static cities of Zagwa and Tibesti, and the highland area known as the Mountains of the Moon.
- The Dead Continent - North America, reduced to an irradiated wasteland by the Sixty Minute War. Rumours abound as to whether it is completely dead or not, which provide much of the focus of Predator's Gold. It is proven not to be completely dead; in the north there are forests with some animals which have managed to survive the Sixty Minute War.
- Asia - The stronghold of the Anti-Traction League. Eastern China was heavily damaged in the Sixty Minute War, and the Himalayas are now the centre of civilisation (the mountainous terrain making it impossible for cities to approach).
- Nuevo Maya - New name for South America, which was severed from North America when "slow bombs" destroyed Central America during the Sixty Minute War. Like Africa and Eurasia, South America is split: static settlements rule the Andes, but the lowlands are filled with ziggurat Traction Cities. Tom and Hester visit Nuevo Maya in the gap between the first two books, but it is never visited in the series itself. Philip Reeve has suggested that if he revisited the Fever Crumb series the story may take place in Nuevo Maya.
- The Hundred Islands - Possibly the islands in the Pacific or the Caribbean Islands. They are mentioned several times during the quartet but never visited directly. It is apparently the home of raft cities as well as Anti-Tractionists.
- Antarctica - Mentioned only once, and is evidently the domain of Oil Drilling Traction Cities. Tom and Hester visit Antarctica in the gap between the first two books, but, again, it is never visited in the series itself.
- Australia - The home to traction cities and small pockets of anti-tractionists, it was set to appear in the cancelled comic The Haunted Sky.
As well as the main quartet, Philip Reeve has also written a prequel called Fever Crumb. The story is set nearly 700 years before the events of Mortal Engines, during the time of the Great Nomad Wars. Traction Cities have not yet been created. The main character is Fever Crumb, an odd looking girl and adoptive daughter of Dr Crumb. This book has its own sequels Web of Air and Scrivener's Moon which detail the reconstructing of London as a traction city and the world pre the rise of traction.