Stephenson is to hard sci-fi as Tolkien is to fantasy. The world he creates in Seveneves is incredibly real, with no detail offered frivolously. It takes a particular sort of genius to dream up and then solve the scientific challenges presented in this book. The only reason I give Seveneves four stars instead of five is that Stephenson rambled too much in the middle of the book, creating (in my humble opinion) unnecessary lulls. There were spots where the writing was a little bit confusing, too. But neither issue would deter me from recommending this book wholeheartedly to others.