In the newly released book Data Points: Vsualizatoin that Means Something, Nathan Yau (Flowing Data blog) shares his ideas on understanding, visualizing, and analyzing data.
The examples are useful and implementable. Many focus on sets of graphs with multiple dimensions of data, rather than a single chart type. The author also presents ideas and examples of solving typical visualization problems, such as visualizing categorical data from three perspectives: discrete categories (bar charts), parts of a whole (pie and 100% bar), and subcategories (tree maps and mosaic plots).
Quick summary: Recommended — great source of ideas on how to think about and communicate data visually. Not too academic, not too nuts-and-bolts — good balance.