Good but not the best book I've read it

This book is a fiction and a literary construction, Dan Simmons is neither a committed writer, nor wants to be a prophet (according to himself). Apparently, many people have missed out on this, so let me write this short text. On his official website:
-is Flashback A Novel Stating Dan Simmons's Political Biases?
-in A word. . . no. In two words. . . hell no.
I put 4/5 because I preferred the Exchequer of Evil and Hyperion ;-). It is a black black black book. This is one of the worst nightmares I've ever read. It immerses us in the near future, 2032, when the Global Caliphate engulfed Europe and Canada (note that it is Shiite in the book, but the new Caliphate recently appeared is Sunni-Salafist ;-)). When Japan returned to the feudal era, when the US and where what remains is independent because the Texas and Mexican reconquista took over the 4 southern states, are a bunch of junkies addicted to a drug, flashback, which can relive past moments, and sells his youth as a mercenary to pay his debts. Within this total and depressing doldrums, a former police inspector, Nick Bottom, is contacted by a Japanese Senior Advisor to solve a non-elucidated murder that took place six years earlier. The detective story is not the best I've read (the 4/5) but the nightmarish universe described by Dan Simmons is living up to what he knows how to write. The details are all darker than each other. Well actually, the real reason for writing this book is called at the end (I will not reveal anything of the plot rest assured): you have to accept reality as it is and not take refuge in drugs. Sage advice. A wise and good reading.