The book does not posit a specific reason as to why the bronze age collapsed. Instead, it lists several factors that could have caused the collapse, and weighs the evidence supporting each. The theory of the book is that many, if not all, of these factors in combination caused a system collapse that led to the upheaval in the titular year. Along the way we get fascinating details such as letters sent between kings, palace intrigue recorded and left to history, and some thoughts on whether the devastation of Troy was part of this general systems collapse.