"Underworld USA" is the last volume of the saga that began with "American Tablaïd" followed by "The Cold Six Thousand". This is a very heavy work in every sense, both because it is a huge pad that weighs his kilo, but especially because it is an uncompromising portrait of an entire segment of American history and I say History with a capital H, because maybe this is what has put off some readers, it happens a lot, a lot, and it's true that writing is not always the most fluid and clearer. Nevertheless, for anyone in the trouble, the latter volume is a treat because the characters are always well crafted, the situations are larger than life, and that is a wealth of information on this period USA. Rare are the writers coming out of the simple framework of polar to offer us something else, and I think Ellroy actually gone. For novices, I nevertheless recommend to start with the Black Dahlia, the most accessible of his books.