For We Are Many

 Bobs go back to earth and discovers they really need help, as a nuclear winter threatens to wipe out humanity. A bob also discovers a planet where there is a life that looks like bats and is primitive but evolving like humans and Bob helps them. Planets need to be terraform and at the end of the book, and Aliens life-form that is a real Von Neuman machine terror ( destroying everything to replicate ) is discovered. 

 It's fun to read but not great literature and the ideas do not go really much places and are not that original.