How to change Safari 6 Reader font? In Safari 5 you could just change the Reader.html file inside of the Safari.app to use a sans-serif font.
This Reader.html does not exist in Safari 6.

How do I manage to change the font of Safari Reader (6)?

I hate to read serif fonts.
Add a rule like this to /System/Library/PrivateFrameworks/Safari.framework/Versions/A/Resources/Reader.html:

.page, h1.title {
  font-family: 'Avenir Next' !important;
}


The !important is required because a .page div has an inline style attribute that overrides the fonts in Reader.html.