I am just starting chapter 2. After delving deep into assumptions in the first third of chapter 1, he had some dull discussion of how ideas move from tentative to accepted, and then a historical summary of fluid statics that was interesting for its tidbits in a field that most physicists don't pay much attention to, but was not very deep in its unpacking of assumptions. It feels to me like Mach wanted to be encyclopedic, and not just give analytical Commentary on key issues.
Chapter two opens with a a declaration that dynamics (the study of moving objects) began with Galileo. Aristotle simply isn't worth Mach's time. It will be interesting to see how this plays out. His encyclopedic goals seem to be balanced by an editorial perspective on significance. Also, he is so encyclopedic that he even goes into an early effort of Galileo's (soon discarded) in which he hypothesized that velocity was proportional to distance. The sheer level of familiarity with primary sources displayed in this work marks Mach as something of a historian as well as a physicist and philosopher.