Book excerpt: Guide to the Presidency is the leading reference source on the persons who have occupied the White House and on the institution of the presidency itself. Readers turn to this guide for its vast array of factual information about the institution and the presidents, as well as for its analytical chapters that explain the structure and operations of the office and the president's relationship to co-equal branches of government, Congress and the Supreme Court. This new edition is updated to include: A new chapter on presidential power Coverage of the expansion of presidential power under President George W. Bush