This book serves an introduction to data science, focusing on the skills and principles needed to build systems for collecting, analyzing, and interpreting data. As a discipline, data science sits at the intersection of statistics, computer science, and machine learning, but it is building a distinct heft and character of its own.In particular, the book stresses the following basic principles as fundamental to becoming a good data scientist: ?Valuing Doing the Simple Things Right?, laying the groundwork of what really matters in analyzing data; ?Developing Mathematical Intuition?, so that readers can understand on an intuitive level why these concepts were developed, how they are useful and when they work best, and; ?Thinking Like a Computer Scientist, but Acting Like a Statistician?, following approaches which come most naturally to computer scientists while maintaining the core values of statistical reasoning. The book does not emphasize any particular language or suite of data analysis tools, but instead provides a high-level discussion of important design principles.This book covers enough material for an ?Introduction to Data Science? course at the undergraduate or early graduate student levels. A full set of lecture slides for teaching this course are available at an associated website, along with data resources for projects and assignments, and online video lectures.Other Pedagogical features of this book include: ?War Stories? offering perspectives on how data science techniques apply in the real world; ?False Starts? revealing the subtle reasons why certain approaches fail; ?Take-Home Lessons? emphasizing the big-picture concepts to learn from each chapter; ?Homework Problems? providing a wide range of exercises for self-study; ?Kaggle Challenges? from the online platform Kaggle; examples taken from the data science television show ?The Quant Shop?, and; concluding notes in each tutorial chapter pointing readers to primary sources and additional references.