I recently received a copy of the an amazing book, Visualizing Density, by Julie Campoli and Alex MacLean. I think it is probably one of the best documents I have run across concerning the ever-thorny issue of residential density. Planners and architects through around terms like units/acre, but it is very often difficult, if not impossible, to grasp a physical picture of what that really means. With hundreds of excellent aerial photographs and diagrams, Campoli and MacLean give clear demonstration of not only what those threshold mean in real world scenarios, but they also provide multiple images of examples of the same density with different methods (single family, multi-family, townhouses, etc.)
This book may only appeal to planning and architect-types, but its emphasis on visual documentation is an essential aide to those of us who are so visually dependent on the synthesis of information. The text accompanying the photos is clear and straight-forward and avoids so much of the current jargon-laden terminology favored by the elite planning class of experts.
For anyone interested in what makes a city and especially how our current cities and suburbs can contain to grow in numbers of people but maybe not in size and still maintain or improve a quality of life, I strongly recommend picking up a copy.