The pool of fire
This is the conclusion of the Tripods series written under the name John Christopher. These young adult science fiction stories are set on Earth ruled by the alien Tripods. A prequel detailing the conquest was added 20 years later.

The series:
0.5 (Prequel) When the Tripods Came (1988)
1. The White Mountains (1967)
2. The City of Gold and Lead (1967)
3. The Pool of Fire (1968)
Children's stories, Science fiction, Juvenile fiction, Human-alien encounters, Teenage boys
Sam Youd
Sam Youd, who wrote under a number of pseudonyms is particularly noted for his works written as **John Christopher** such as the *Tripods Trilogy* or the *Sword of the Spirits Trilogy*.

Sam Youd was born in Huyton, Lancashire (though Youd is an old Cheshire surname). He adopted the name Christopher Samuel Youd for his professional writings, leading to the widespread but mistaken belief that that was his birth name. Throughout his life he was known simply as Sam to his friends and acquaintances.