Second book of the Tripods trilogy, where the plot thickens in darker ways.
For all their resistance, the people of the White Mountains barely know anything of the tripods. Who they are, what their plans are, and how they can fight them. So they devise a plan, win the annual games of the Capped, the games where Will lost Eloise to the tripods in the first place. Get taken, spy on them, and come back alive.
Will, Beanpole, and a boy named Fritz are chosen, and after several dangers, they arrive at the games. While Beanpole is left behind, Will and Fritz are chosen, and taken inside a tripod.
They wake up in a hellish city of gold and lead, where the heat is oppressive, and gravity crushes them. They are now servants of the Masters, and Will and Fritz soon become aware the Masters of the tripods have a much darker plan than they ever thought.
John Christopher set the standard for children's dystopia books with this series, and this book is no exception. It's brief, but every word is well chosen, and it's not serious or cute. It feels a little bleaker than the first book, with the capped no longer being entirely cheerful, and the ultimate plan of the aliens for the future of mankind being very grim. But it's not one-sided, and that adds to the horror: Will's very sympathetic Master is the vessel of many of the horrors in the book.
Definitely recommended, and finish the series with the Pool of Fire.