There is no commercial interest behind this book. Therefore, it is made available as a PDF free of charge for download and may be passed on according to the CC license (in the book).
In addition, there is also a print version, which is essentially given at cost price:
Price: € 5.00*
Price: € 1.99
Published by BoD
Available for instance in the BoD-Shop
Free Download of the PDF: https://drive.google.com/file/d/1-mSdIi1BgiNMjCatTAfLDeasJkGXdFrl/view?usp=sharing
* In comparison to the German edition, I raised the print version's price from 4 € to 5 €. The German version obviously was too cheap for the liking of amazon, so they do not distribute it, but claim, that the printed version was not available. Some feature of neoliberalism, isn't it? If it brings no profit, it's no good ... I am really sorry ...