Courtney Freer‘s new book Rentier Islamism: The Influence of the Muslim Brotherhood in Gulf Monarchies (Oxford University Press, 2018) contributes significantly to an understanding of one of the most controversial political groups in Middle East politics. Widely viewed as a player that cannot be excluded from the political process in the region, the Muslim Brotherhood is at the crux of political conflict, particularly in Egypt, where its president, Mohammed Morsi, was toppled in a military coup in 2013, and in the Gulf where it is at the crux of a dispute that has pitted Qatar against an alliance led by the United Arab Emirates and Saudi Arabia.