This is a huge book (made up of three smaller books), and a huge achievement. Unfairly overlooked nowadays, John Dos Passos's novel is well worth your time.
The three novels here make up one large whole. The book is made up of stories following the lives of various characters from all walks of life. Their lives sometimes intersect, sometimes get better, sometimes get worse and even sometimes end.
In between these stories are shorter experimental pieces: 'The Camera Eye', which is Whitman-esque description of scenes; 'Newsreel' which is a collage of headlines and journalism, to give an idea of the events that are going by as the novel progresses; and Biographies of famous people of the times, millionaires (eg Hearst, Carnegie), creative people (eg Edison, Lloyd Wright), activists (Eugene Debs, Joe Hill), and many others. The biographical sections are very impressive. Done in a style that is half poem, half telegram, they concisely and accurately sum up famous personages, some you will have heard of, some you won't.
As the novels goes by, you are completely transported into the early 20th Century. Dos Passos is very critical of modern life here; he seems to feel that the modern system that is being put in place will not make anyone particularly happy. This is not to say that the book is depressing, but it is convincingly realistic, which is not always pretty.
The book ends with the Sacco and Vanzetti trial, which the author depicts as the event that should spark a revolution. This is incendiary stuff - but Dos Passos makes a good case. His politics are not thrust down your throat. It's more a case of showing than telling.
Sacco and Vanzetti are probably as forgotten today as the novel U.S.A. is. A read of this novel could make you think both deserve wider recognition. If you want to immerse yourself in another time, and learn a little along the way - or if you simply want an entertaining read - this is the book for you.