Our universe seems strangely ''biophilic, '' or hospitable to life. Is this happenstance, providence, or coincidence? According to cosmologist Martin Rees, the answer depends on the answer to another question, the one posed by Einstein's famous remark: ''What interests me most is whether God could have made the world differently.'' This highly engaging book explores the fascinating consequences of the answer being ''yes.'' Rees explores the notion that our universe is just a part of a vast ''multiverse, '' or ensemble of universes, in which most of the other universes are lifeless. What we...