The author is highlighting the fact that the 9/11 attacks were very personal experiences that changed their lives and identities, not just distant historical facts. The main idea of the book, the profound and personal effects that historical events like 9/11 have on people and communities, is encapsulated in this quotation. It especially addresses the concerns of the students who do not understand the significance of historical events and how these events impact their lives and the lives of the people around them.