Every chapter starts with a thesis.
Not a summary. Not a TL;DR. A single proposition the chapter is going to defend. You know what you're reading, why, and whether you need it — by the end of the first page.
Eyebrow labels for quick scanning. A lede in a type size you can read from a metre away. An accent colour chosen per volume, used sparingly, never for decoration.
Set in Syne display, Inter body, JetBrains Mono metadata. Edited to the standard of a paper book.