Perhaps the most practical section is the OCAP flowcharts. The PDF provides templates for "If the control chart shows Rule 1 violation (beyond 3 sigma), do this..." This turns abstract statistics into actionable maintenance tasks.
You might think that with the rise of Artificial Intelligence (AI) and Industry 4.0, a standard from the early 2000s is obsolete. In reality, IPC-9191 is experiencing a renaissance. Ipc-9191 Pdf