The Whole Shebang
Plenty of books try to explain the origin of the universe, but despite the ascendance of the Big Bang theory, numerous details of that theory remain in flux as new observations are made and new hypotheses formed (and then confirmed or rejected). Timothy Ferris's The Whole Shebang is an up-to-date account of the various mechanisms believed to have contributed to the universe as we now know it, from the Big Bang itself to inflation to superstrings. The Whole Shebang eschews mathematics and formulae and explains cosmological concepts in clear and enticing prose. If you need an update on the state of the universe, you'll find it here.
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