The Sky is Falling by Lester del Rey is a science fiction novel that explores the idea of a society on the brink of collapse due to the forces of both internal and external threats. The protagonist, Dave Hanson, finds himself thrust into a world where civilization has regressed, yet advanced technology from a forgotten era offers hope for survival. As the story unfolds, Dave must navigate a complex landscape of time travel, shifting realities, and existential danger. Del Rey weaves themes of human resilience, the consequences of technological dependence, and the potential for rebirth from societal ruins.