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However it is a long book and I do think that the readers are presented with too many different ideas to get them clear in their minds. For instance 'Parallel Worlds' may refer to (i) Universes budding off our current one, (ii) Higher dimensions in physics (branes and the like) or (iii) Many worlds quantum theory. Many books fail to distinguish between these, and I hoped that this would do better, but I don't feel that it did. So the book is fine as an inspirational overview of the area, and a must for prospective sci-fi authors, but I would advise a reader wanting a starting point to study the physics to look elsewhere.