The German friend also recommended me the book "The Creature from Jekyll Island" by G. Edward Griffin. It is about the history where central banks played significant roles in waging wars and exploiting people especially in the UK and the US. They have allegedly detached their money from the true value such as gold, attached it to mere paper and manipulated it by inflating and deflating "money supply". The book was somewhat shocking to me, for it displayed many an evidence documentation indicating the governments and corporates have conspired to make wars, revolutions and depressions happen to profit from them.
I like this book very much because it is mental intriguing, but I hate it when I have to explain the book to my friends because I always sound like I am talking about a dubious conspiracy theory.
When I look into related articles, I bumped into a book called "Meltdown" by Thomas E. Woods, Jr. The book is a recent bestseller in US and also covers "Lehman Shock". Woods is a scholar from "Austrian School", the most famous from which is Friedrich Hayek, a former Nobel Prize Laureate in economics. This book is non-conspiracy but very critical of the central banks along the same line with "The Creature from Jekyll Island". They have also had significant influence on Ron Paul who is a Libertarian congressman from Texas that wrote "End the Fed".
This is the book that explains the current economic situation excellently and I have recommended all my friends to read it.