text: Lee Smolin is a very deep thinker and original physics theorist, ready if needs be, to question cherished assumptions. One is humbled at how fertile his mind is and how he is familiar with the ideas and the research of so many people
  
  The book is mainly an account of his misgivings about string theory, where he initially states, as he sees it, the five big problems in physics. In this context, he makes the very important point that since the end of the 1970's there has not been a single breakthrough in our understanding of elementary particle physics and, in particular, he claims string theory does not achieve such a breakthrough. 
  
  In making his case against string theory he discusses what string theory has given and shows how it appeared to offer a solution to some of the problems of theoretical physics. But then he builds up his case against the theory. He says that string theory does not reproduce the standard model, probably the most successful theory in physics, but even predicts particles not seen in nature. It did not predict and does not cater for dark energy, nor does it make new precise and falsifiable predictions. In particular he says string theory does not offer a solution to the foundational problems of quantum mechanics.  He also notes that here is no complete formulation for string theory. He shows though how the five versions of string theory could be unified if membranes rather than strings were assumed, but notes that this theory, M theory, still remains a tantalizing conjecture. He says hopes for a unique string theory have receded.
  
  This reviewer would not dare to comment on his assertions but will say that any assertions he makes, are based on a very thorough knowledge of modern theoretical physics and merit the full consideration and respect of the reader. Indeed new ideas are needed in physics as Lee Smolin says. We are missing something big. There is a feeling though that we are on the verge of that big breakthrough - that something just beyond our understanding at the moment will surface through the `murk' into our consciousness and revolutionize our knowledge of nature. The clues are there. To do this, Lee rightly says that the sort of people who see through universal assumptions and ask new questions are needed. He also says that progress sometimes requires deep philosophical thinking but sometimes does not. And whether it is `lateral' thinking or a breakthrough revolution in `conceptual' thinking, new thinking is definitely required. Lee concludes his book saying that what he intends to do is just that. He chooses to start with a paper of his on the relationship between quantum and thermal fluctuation. A good choice perhaps. 
  
  I strongly recommend that anybody who is interested in physics and the current problems and mysteries in the area to immediately buy this book, if they have not already done so.
  
  
  
  
  
  
  