I found this book at Barnes & Noble on the bargain table: Physics of the Impossible by Michio Kaku. I thought this book was very interesting and thought provoking. The author takes a look at different things that are often mentioned and promoted in science fiction novels and he discussed whether or not the impossible could ever be possible. Some of the things discussed are things you may see in Star Trek or Star Wars like: teleportation, star ships, laser guns, time travel, etc. He has divided these various impossibilities into three categories. Category one impossibilities are things that are impossible now but do not violate the laws of physics and may be obtainable in a couple of 100 to 1,000s of years. Category two impossibilities are things that are impossible now but do not violate the laws of physics and may be obtainable in several 1,000 to millions of years or more. Category three impossibilities are things that are impossible now and if anyone ever figures out a way to achieve them then the laws of physics would have to be rewritten. The book can be a little technical at times and the author often has to talk about things that are completely theoretical (and sometimes it is difficult to sort out if something is entirely theoretical physics or established physics).