Carl Sagan viewed space exploration as both a natural consequence of our nomadic past and an essential constituent of our survival: in Pale Blue Dot, he articulates this vision, making an elegant and compelling argument for a programme of sustained space-exploration in order to cheat the cosmos of humanity's ultimate extinction.
Given Sagan's prodigious output over an all too brief life, recycled material from earlier work is to be expected and the book opens with one of his recurrent themes, revisiting the idea that science continues to diminish humanity's over-inflated sense of importance and plots our species' ignominious ("great" ch.3 pp.20-37) demotion from cosmic "purpose" to universal bit part. Sagan also covers other favourite topics, including global warming and weapons of mass destruction, synthesising these themes into a comprehensive argument that humanity has reached a turning point in its evolution with the ability for self-destruction without, perhaps, the wisdom to prevent it. However, whilst some of the early content may feel familiar, this is not a simple rehashing of old arguments: it is a grand vision of humanity's future and, with his characteristic clarity and restraint, Sagan makes a powerful argument that our innate curiosity will eventually drive us to the stars.
For obvious reasons, the space exploration review appears a little dated but Sagan's intimate involvement with much of America's attempts to explore our solar system and unique ability to collaborate with Soviet scientists makes it a fascinating and insightful read nonetheless. Moreover, the discussion is really a vehicle for Sagan's speculations about the potential for such adventure and he proceeds to indulge his imagination for cosmic housekeeping, boulder hopping and interplanetary squatting! This book can leave no doubt that Sagan was a true visionary and his premature demise is a loss to us all.
Perhaps not quite as good as The Demon-Haunted World, but very, very close!