Book excerpt: The first edition of this book was written by Jeffrey Schox for his course "Patent Law and Strategy for Innovators and Entrepreneurs" at Stanford University. After an introduction to intellectual property, it explores the patent system, the requirements for a patent, infringement, and inventorship and ownership issues. The second edition included the America Invents Act ("AIA"), which transformed the U.S. patent system from a "first-to-invent" system to a "first-inventor-to-file" system. The third edition added a glossary and general edits. The fourth edition includes five additional cases: KSR (Supreme Court 2007), Stanford v. Roche (Supreme Court 2011), Prometheus (Supreme Court 2012), Nautilus (Supreme Court 2014), and Limelight (Fed. Cir. 2015).