This book started as a collection of my teaching notes for the ECON 52 course that I taught at Stanford University. The objective of that course, and of this book, is to introduce students to the ideas and way of thinking of modern macroeconomics in a unified way that is accessible with a moderate amount of maths. Modern macroeconomics emphasizes explicit microeconomic foundations and general equilibrium analysis, combined with various kinds of constraints and market imperfections. When preparing the class I thought none of the existing textbooks conveyed this in a way that I liked, so I prepared my own notes, which then grew into this book. While mostly self-contained, the book is probably most useful to students who are familiar with the basics of multivariable calculus and have taken a calculus-based microeconomics class.