the tripods trilogy. follows a young teenage boy in a post-apocalypse where aliens have taken over the earth and put mind control caps on all the adults. the boy has to first travel to join a resistance group, then he infiltrates an alien city, they mount a desperate last stand etc

John Christopher is the author. there’s a prequel book too, so four in total

There’s a prequel⁉️

yeah! it’s the story of how the takeover happened. imo not quite as fantastic as the trilogy but still worth finding

ME WANT NAME OF BOOK SERIES