If I could recommend one book for any American to read, it would be Still the Best Hope by Dennis Prager. Prager is a nationally syndicated radio talk show host and author of the book: Think a Second Time.
In Still the Best Hope, Prager explains that there are three ideologies competing in the world: Leftism, Islamism, and Americanism. He thoroughly explains with convincing arguments how both Leftism and Islamism both fail to make a decent society. Moreover, he makes the case for American values. He explains how Americanism is the best system ever devised to make a good society.
I believe every American should read this book. This book is designed for Liberals, conservatives, or anybody in the middle. If you want to know what America stands for, this should be the book to read.
The book can be purchased here: http://www.amazon.com/Still-Best-Hope-American-Triumph/dp/0061985120