Printed books generally attract a reduced or nil VAT rate, in accordance with the EU VAT Directive. However, this was caste prior to the emergence of digital books. Countries diverge on their treatment of ebooks for VAT - countries such as Germany and the UK apply their full VAT rates. But countries like France and Luxembourg charge reduced rates.
In particular, Luxembourg charges 3% on ebooks since the start of 2012. Luxembourg is the European home of Amazon, which can therefore only charge 3% VAT on ebook sales to consumers in any EU country. The leaves ebook sellers in countries like the UK at a disadvantage.