•Why it earns a slot
Why it earns a slot: it's the hinge book where Nietzsche breaks from Wagner and metaphysical system-building for good, replacing grand theory with hundreds of small, testable psychological observations.
Nietzsche invents a fictional audience of "free spirits" just to survive writing a book that reduces virtue, vice, and even sainthood to ordinary human chemistry.
This distillation is written from the freely available original, which is always the better read when you have the time: Project Gutenberg.