The Boeing 737-800 is a marvel of engineering, but it is the procedures inside the QRH that make the aircraft truly safe. It represents decades of lessons learned, test pilot data, and engineering expertise condensed into a format that fits in your hand.
For general public or student pilots (non-airline): boeing 737-800 qrh quick reference handbook
The Boeing 737-800 is a "Classic" NG (Next Generation). It differs significantly from the Airbus A320 (which uses an ECAM system that automatically displays procedures). On the Boeing, the computer tells you what failed (via EICAS alerts), but it does not tell you what to do about it. That is the QRH's job. The Boeing 737-800 is a marvel of engineering,
Boeing designs these checklists using a highly structured philosophy to minimize human error under stress: test pilot data