“The Guest Book” is the much-anticipated return of Sarah Blake (The Postmistress).  Her new story    follows three generations of a privileged American family, one used to running the world. By the end of the novel, they’re beginning to be run by it.  Their fortunes are symbolized by their island home in Maine.  For generations, it has been a symbol of their position and solidity.   As the story reaches its climax, it is uncertain if they can hang on to it. Meanwhile, the family secrets are coming out of the family closet.