This is one of the reasons (given, anyway) ebooks are more expensive than print.
If you're a UK resident, you can add your name to a petition to change this.
The petition introductory page probably makes a better argument:
Paper books are free from VAT despite their impact on the environment yet e-books carry 20% VAT. Paper books need oil based inks and glues, high energy use for paper production and printing, oil fuel for distribution and large land use for warehousing. At the end of their lives many find their way to landfill. E-books are far more environmentally friendly using a tiny fraction of the energy of a paper book for production, distribution and storage and at the end its life it is simply deleted. A book should be defined by what it provides not the material that is used to produce it and the more environmentally friendly version should be encouraged and not discouraged by VAT.
You can sign the petition here.