Readers will learn fascinating facts about America's most secure sites and structures. Air Force One shares details (its business office, gym, and kitchen) about the airplane built to keep presidents safe, but keeps a lot secret.mostly because the defenses on this plane are a secret to everyone but its personnel. Underground storage vaults protect high-value or rare physical objects, but can also employ digital protection using super secure servers. Fort Knox is one of the most secure places on Earth and for good reason; it holds over 5,000 tons of gold. Trivia at the end of each book offers extra jaw-dropping facts; suggested activities extend learning beyond the book. VERDICT A fascinating look at amazing high-security measures. A highly recommended series.