This Math-Free book is a good introduction to quantum gravity and has a lot of interesting history about the development of the theory since 1899. It's an informal introduction to a very difficult and doubtfully intelligible theory doubted even by its most ingenious contributors. The reader should expect that he/she will have to concentrate hard on what Balungi says but the rewards are significant. He is a talented physicist and a good writer. If you read it carefully and stop to think about the message as it unfolds then you will get a worthwhile if imperfect picture of what the theory is saying and how it was invented, It's buried treasure and you will have to do some digging. It is a really serious attempt to do all that can be done in an informal style. Balungi explains and re-defines Einstein's theory of general relativity, quantum mechanics, black holes, the complex architecture of the universe, elementary particles, gravity, and the nature of the mind. This wonderful and exciting book is optimal for physics graduate students and researchers. Not since Stephen W Hawking's celebrated best-seller Brief History of Time and Richard P Feynman's QED: The Strange Theory of Light and Matter has physics been so vividly, intelligently and entertainingly revealed.This is a Second Edition to Quantum Gravity in a Nutshell