A clever idea. I think that the use of maps to depict the spatial relationships by which we organize complex, non-spatial concepts is still vastly under-explored. This is especially true in light of the tedious nature of linear narratives that seek to explain complex relationships among multiple subjects. A lot of legal concepts, for example, could probably be better explained with maps than by treatises, but the tyranny of the printing press goes on.
This map, showing French wine regions and their signature grape varietals as stops along a series of fictitious subway routes, bridges an attempt to map what are primarily nominal relationships with the more traditional subject matter of cartography. Typically, the sample JPEG from the publisher is very reduced: You would have to purchase the full-sized print to enjoy most of its details.