Amazon.co.uk seems to be running all its EU sales of eBooks through Luxembourg, because it only charges 3% VAT on eBooks. Good on them! In the UK there is no VAT on physical books and full VAT on eBooks. I assume this is done to benefit the paper industry and the oil industry.
In the US 'Items sold by Amazon.com LLC, or its subsidiaries, and shipped to destinations in the states of Kansas, Kentucky, New York, North Dakota, or Washington are subject to tax'. Other states to not, I think, have a sales tax on eBooks.
Someone should explain to the people who write tax codes that, digitally, there will only be one world, however many 'Chinese walls' exist at present.