Introduction to Data Science, an open source book

Introduction to Data Science, by Harvard biostatistics professor Rafael A. Irizarry, is an open source book that provides, as you might have guessed, an introduction to data science:

The demand for skilled data science practitioners in industry, academia, and government is rapidly growing. This book introduces concepts and skills that can help you tackle real-world data analysis challenges. It covers concepts from probability, statistical inference, linear regression, and machine learning.