'In spite of its sociological success string theory is still far from a solution of the problem of quantum gravity which should be considered as wide open. The book of Carlo Rovelli provides the basis, both at the technical and the conceptual level, for research in this fundamental problem of physics. The basic issues are clearly and deeply analyzed without any dogmatic stand and with great freedom of thoughts resulting in an invaluable opportunity to learn and think for both mathematicians and physicists.' Alain Connes, Collège de France, I.H.E.S. and Vanderbilt University
'This is a truly great book! … a must for someone interested in quantum gravity.' Mathematical Reviews
'… written very carefully and can be recommended highly to anybody interested in the broad field and in conceptual issues of quantum gravity … experts … will find many new and clear notes of the author's view of loop quantum gravity as one of its founders … a non-expert reader, after working through the book, will be well prepared to read up further details in research or review articles …' General Relativity and Gravitation Journal