The Right to Know is a timely and compelling consideration of a vital question: What information should governments and other powerful organizations disclose? Excessive secrecy corrodes democracy, facilitates corruption, and undermines good public policymaking, but keeping a lid on military strategies, personal data, and trade secrets is crucial to the protection of the public interest.

Over the past several years, transparency has swept the world. India and South Africa have adopted groundbreaking national freedom of information laws. China is on the verge of promulgating new...