Deutsch is best known for his views on quantum computing and its link to the many worlds interpretation of quantum mechanics. Naturally these subjects figure highly in this book, but I would say this isn't just a book about modern physics, in fact it's more of a philosophy book. If that's put you off then it shouldn't - this is philosophy as it should
be written. In a non-technical and highly readable way, Deutsch puts forward the arguments for his view of the nature of reality, and I have to say that he is fairly persuasive - even for people like me who don't believe in the many worlds interpretation
The double slit experiment is introduced early in the book and is central to his arguments for the multiverse - he shows how this leads to the conclusion that light is being influenced by photons from other universes. He then links this in an intruiging way to the other three strands of his philosophy, which are evolution, epistemology and the theory of computation. He goes via virtual reality, time travel and his own solution to the problem of induction, and concludes that we aren't just here by chance, rather intelligent beings are an integral part of the universe.