My favorite cartography book is Eduard Imhof’s Cartographic Relief Presentation. A few years back I picked this book up (translated to English) from ESRI press for $75 if memory serves me. Now it can be gotten for much cheaper.
Imhof spends a lot of time on feature simplification and separation, a problem which keeps me up at night. For example, if you have a lot of overlapping and/or touching contours, what are the local distortions and simplifications that can be done to enhance map readability?
This problem applies to other overlapping features, such as a road following a river, where at a given scale one might not distinguish between the two, so we exaggerate their differences, in this case, while maintaining their basic topology.
I’ve played with this problem before, but now I’m considering a new approach. I pinged Martin Davis of JTS fame for some advice. He suggested using force directed layout to solve this problem, much as he does in JTS Test Builder for magnifying/investigating topology.