If you are a new SolidWorks user, the chapters of Part I are essential. I recommend reading these chapters in order because the material in each chapter builds on the material of the previous chapter.

If you are an existing SolidWorks user, I strongly recommend Chapters 2 and 5 because the interface has changed significantly since 2007. Even if you are a very experienced user, I recommend Chapter 5. The visualization techniques are things we all use on a constant basis in the software, and picking up even a small tip can add to your productivity dramatically.