Writer Lucy Hughes-Hallett, who heads the jury panel, said a theme of many of the books was "migration -- the pain of it, but also the fruitful interconnectedness of the modern world."
The six finalists are set to be revealed on 22 April and the winner on 2 June.
The International Booker Prize is awarded every year to a book of fiction in any language that is translated into English and published in the U.K. or Ireland. It is run alongside the Booker Prize for English-language fiction.
The prize money is split between the book's author and its translator. Ngugi translated his own novel from his mother tongue, Kikuyu.