Outline indentation for the book is confusing

I find it confusing that, in the outline view, the chapter headings and section headings look the same: same indentation and same font size. It would be better if either the section headings were indented or rendered in a slightly smaller font.

Locate the book's outline-view entry point and inspect how chapter and section headings are rendered. Compare the existing indentation and font-size styles, then verify the chosen distinction in the outline view; done means the hierarchy is visually clear.

Written by the indexing model from the issue text.