Barthes wrote Rhetoric of the Image in 1964. Here it is set in Garamond, how theory usually looks.

Next to it, the same text in San Francisco, how theory looks at 2 a.m. on a phone.

Barthes divides an image into three messages: what is written, what is shown, and what it quietly wants from you.

The layout is made of exactly these three. So when you look at the pages, you are already doing the analysis.