Thinking a lot about visual communication in technical writing. What should I read?

Is there anything like “Understanding Comics” but more a focus on explanation rather than narrative?

The val.town site got me thinking about this. I love the gestalt quality of things like this — cheat sheets, one-pagers, poster presentations, etc.

To clarify, I’m particularly interested in non-sequential explanation. Most of the non-fiction comics I’ve seen still rely on sequential exposition.

(Of course there are still lots of interesting non-sequential aspects in the page and panel layout)