Under pressure from left-wing journalists and activists, Amazon is purging right-wing authors from its store, including a book co-authored by English Islam critic and independent commentator Tommy Robinson.

The web retail giant has become the dominant market player in book sales, accounting for nearly 50 percent of physical and 83 percent of e-book sales in the U.S. As such, Amazon has the power to effectively cut an author off from the vast majority of the books market.