This book is massive. With more than 20,000 lines of code and 150,000 words of text, a printed version would cover more than 1,200 pages of text. Obviously, we do not assume that everybody wants to read everything.While the chapters of this book can be read one after the other, there are many possible paths through the book. In this graph, an arrow $A \rightarrow B$ means that chapter $A$ is a prerequisite for chapter $B$. You can pick arbitrary paths in this graph to get to the topics that interest you most:But since even this map can be overwhelming, here are a few tours to get you started. Each of these tours allows you to focus on a particular view, depending on whether you are a programmer, student, or researcher.