This book is in the 'Introducing ...' series of 'comic books'. It's excellent. Perhaps the best thing about it is the structured way in which it describes the development of quantum theory. After being introduced to the key scientists, the reader is told about the nineteenth century developments from which quantum theory arose. It emerges that there were three problems facing classical physics around the year 1900. These were solved by Max Planck, Albert Einstein and Niels Bohr respectively and, in the process, quantum theory was born. The author deals with these problems and their solutions in detail. I found this to be a very clear approach, which seemed to lay things out in chronological order with everything fitting in to place.
After this the author goes on to describe the further work of Niels Bohr as well as that of Wolfgang Pauli, Louis de Broglie, Max Born, Werner Heisenberg, Erwin Schrodinger and Paul Dirac. Schrodinger's cat and wave-particle duality are described along the way, the theory of QED gets mentioned but is not described, and the book culminates in an account of the EPR paradox, Bell's inequality theorem and the work of Alain Aspect.
Having said all that, this is not an easy book. I don't think it would be possible to write an easy introduction to quantum theory. I had to read it a few times to understand it (and there are still quite a few pages I don't understand), but I learned a lot in the process. There is an amazing amount of information packed into this book and even someone who is scientifically knowledgable would benefit from it. If you know nothing or little about quantum theory, you're not going to find an easier introduction or one so well organised, and even if you only understand half of the book, you'll learn a great deal.