Universe or Multiverse?
Bernard Carr
Cambridge University Press
One answer to the question about us being the only intelligent life in the cosmos is answered by the multiverse theory of multiple universes. This is a subject that has received a lot of thinking and mathematical analysis in recent years. Recent developments in cosmology and particle physics, such as the string landscape picture, have led to some serious thinking that ours is not the only universe. 

This book has papers from a number of active and eminent researchers in the field, mainly from cosmologists and particle physicists, but also from such diverse fields as philosophy. The papers cover the complete spectrum from enthusiastic support to outright scepticism. There is very little advanced mathematics in the book when compared with some other texts on the subject.