Smolin surveys the current state of fundamental theoretical physics and finds some problems. String theory has dominated the field for decades but has yet to produce a new experimental prediction. Furthermore, there is no real string theory as such, but rather an enormous number of possible theories which may or may not be unified under the even more speculative M-Theory.
Smolin challenges the scientific community to embrace alternate approaches to fundamental physics and introduces a number of them, some he has worked on and others he has not.
This is a very, very good book.