Since issues of open space are so important to the idea of a sustainable city, you might be interested in a book written by one of the nation's experts on open space and published by the Trust for Public Lands. Peter Harnik's book Urban Green: Innovative Parks for Resurgent Cities, looks at ways that "built-out" cities can make commitments to adding green space.
The book's description says:
"Urban Green explores new and innovative ways for 'built out' cities to add much-needed parks. Peter Harnik first explores the question of why urban parkland is needed and then looks at ways to determine how much is possible and where park investment should go. When presenting the ideas and examples for parkland, he also recommends political practices that help create parks.The book offers many practical solutions, from reusing the land under defunct factories to sharing schoolyards, from building trails on abandoned tracks to planting community gardens, from decking parks over highways to allowing more activities in cemeteries, from eliminating parking lots to uncovering buried streams, and more. No strategy alone is perfect, and each has its own set of realities. But collectively they suggest a path toward making modern cities more beautiful, more sociable, more fun, more ecologically sound, and more successful."
I have always found Harnik's work to be very useful and insightful.