[theducks]

Originally Posted by FelixKrull

At the moment I use "Remove Font-family" and remove "line-heigh", and

@page { margin: 0 !important; }

html, body {
  margin: 0 !important;
  padding: 0 !important;
}

(suggested by AI)

I just saw that I also could remove "margin-left" and "margin-right" (I am not very good at css though)

Most novels for example do not have blockquotes and I would not really care about chapter headings, but big margins on my Kindle are really annoying.

So one has to work on the books Css directly I presume?

IMHO that usually is the fastest way to wade thru a garbage (like you have) CSS

Keyword: to understanding a CSS function: Box Model
BTW In the Calibre Editor. View: Inspector.
That even shows the model. If you expand the code ► you can select that line and the Box will show the 'effective' cascaded value, and you can backtrack to the cause . Really handy when the cause was levels deep.