Central Banks around the world are continuing to research Bitcoin and crypto-currencies. Recently we have seen the Singapore Monetary Authority issue a study into the possibility of issuing the SGD on a blockchain.
I read all these reports and the best one so far was issued on 5 September 2017 by the Bank of Finland. Titled 'Monopoly without a monopolist - an economic analysis of the bitcoin payment system', the 52 page report is full of complex economic, mathematical and game theory analysis. However, even if you do not wish to wade through the main body of the report, the introduction, the description of the Bitcoin system and the conclusion are very informative.
One quote from the conclusion 'It's apparent functionality and usefulness should further encourage economists to study this marvelous structure.'
Also 'Bitcoin is not regulated. It cannot be regulated. There is no need to regulate it..."
The report is here.