Why not try reading it? Or, you know...google it? Thirty second search can find you a trove of answers to stupid questions (of which you have plenty).
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"Stephen Hawkings' book A Brief History of Time was published in 1988. It aimed to make complex concepts in theoretical physics accessible to a layman's audience. The book was a great success, guiding readers through topics like the Big Bang, the fabric of time and space, particle physics, black holes, and more.
It is a non-fiction book that takes care not to use technical terms without first explaining them. A simple summary of A Brief History of Time goes all the way from the beginning of the universe to its end, explaining things like space and time, the expanding universe, the uncertainty principle, black holes, wormholes, and time travel along the way."
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It is a book on physics/astrophysics. Hawking wasn't nearly as interested in the possibility of alien life as Carl Sagan was. He was purely a mathematician and astrophysicist in his career life. His book was about the physics of the universe and spacetime, and the objects in it. Not aliens, or anything about biological life.