Kaku's Parallel Worlds is out soon (Penguin). It considers the possibility of travelling from our universe to other universes through wormholes and black holes.
He is reading about supermassive black holes in The Edge of Infinity by Fulvio Melia (Cambridge, 2003). "It is truly remarkable that, before our eyes, just in the past decade or so, thousands of black holes have been tentatively or conclusively identified in the universe. Eventually, astronomers hope to find the holy grail of black hole physics - a sensor reading indicating the presence of the event horizon itself. Perhaps then one may begin to ask the deep questions about black holes: do they emit radiation? Is information truly lost?"
Important books? Science and Ultimate Reality, edited by John Barrow, Paul Davies and Charles Harper (Cambridge, 2004), looks at the great unsolved problems in quantum theory, including the famous Schrödinger's cat problem: can the cat be ...
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