The book presents a modern approach to understanding U.S. antitrust law, illuminating the economic analysis that dominates modern antitrust analysis in a straightforward way that minimizes technical jargon and makes the underlying economic concepts accessible to a broad audience. The cases are carefully edited to present the facts and issues clearly and succinctly, and the book includes detailed textual answers to all the tough questions and details how to apply modern antitrust economic analysis to the cases. The result is a book that is relatively compact, around 900 pages, but covers the full waterfront of antitrust issues and generates plenty of multi-layered points and ideas to fill a class. Throughout the book incorporates important Supreme Court antitrust cases and agency guidelines. The merger section focuses on modern agency practices and merger theories, and selected cases that illustrate them, rather than on outdated Supreme Court cases that no longer describe current merger enforcement. The fourth edition also updates the book to incorporate recent developments, including the decisions in NCAA v. Alston, Ohio v. American Express Co., and United States v. AT&T, Inc. (the ATT-Time Warner merger case), and the 2020 Vertical Merger Guidelines and their withdrawal, along with detailed analysis of those new developments.