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Title: Great book but now out of date
Review: I've noticed the rave reviews (some very recent) below don't take note of how the book was written in 1995 and is now discredited. (No discredit to Kaku personally, of course.) The various 10-Dimensional superstring theories have now been shown to be a minor part of a greater theory, 11-dimensional M-theory. No doubt Kaku will explain this too in due course, but until then remember the theory in this book's no longer valid.
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