ZXX typeface is played out throughout the book in headings, chapter markers, and navigation. It is designed to obfuscate the meaning of the written characters for OCR software and machine intelligence. ZXX is a hero of Part 2 of the book that provides a deeper context for its usage.
Knockout is used for body copy and secondary narrative. One of my favorite typefaces for its versatility — it has 32 weights that differ from very condensed to very expanded and from hairline to black. I picked a slightly extended version (HTF32) for body copy as it reads better over various backgrounds and a condensed version (HTF31) for secondary narrative as it has to fit in a tight space.
Clean, simple versatile, yet powerful color combination lets the chapter content to shine while establishing the right tone for different chapters.