It's exciting to see books come out that address these issues. Astrobiology and astrosociobiology remain proto-sciences deeply rooted in the philosophical and speculative realms. Thinkers like Grinspoon, Milan Cirkovic and Stephen Webb are bring these issues to light, and hopefully they can be expanded upon into testable and provable hypotheses. I particular like Grinspoon's idea of developing a "natural philosophy of extraterrestrial life" -- it's somewhat reminiscent of my idea of astrosociobiology, which is essentially an attempt to find the hard biological, physical, social and environmental factors that circumscribe the development of all intelligent life in the Universe.
Here's a description from his Website:
Lonely Planets is a funky natural philosophy of life in the universe written with authority and edge. Dr. Grinspoon uses the topic of ET life as a mirror in which we view human evolution, history, present, and future in cosmic perspective. With an accessible, breezy and often whimsical style, he presents an authoritative scientific narrative of cosmic evolution along with provocative ruminations on how we fit into the story of the universe. In illustrating how we - scientists and nonscientists alike - have projected upon alien life our own philosophies, biases and preconceptions, he exposes the assumptions we make about extraterrestrials, and how these illuminate science and its limitations.
Writing from the perspective of a working scientist who has helped to shape modern planetary exploration, he does not shy away from the spiritual dimensions of the question of ET life. Rather, he shows how both scientific research and "new age" searching on the topic of aliens serve the same deep spiritual urge. Lonely Planets concludes with an impassioned and hopeful description of how a synthesis of our scientific and spiritual capacities can insure our survival into an attainable and wondrous future.