Enter a term in each of the first two windows of the Advanced Keyword Screen below.  Try peace and "south africa".  The quotes around south africa gives you those tow words adjacent to each other in that order. 

Refine your search by changing the search windows to Title.  Do that by clicking on the dropdown arrows to the left of each window.  Books with those terms in the titles will more likely address the subject substantially.  But you may get too few hits as well.

You can also try using Subject categories, instead of Keywords.  Subject categories are official terms created by the Library of Congress used by catalogers to organize our material.  The following are all official Subject categories:  peace-building, human rights, and economic development.  Change one of the search windows in the Advanced Keyword Search window below to Subject by clicking on the dropdown arrow to the left.  Then enter one of these three Subject categories.

MARQCATplus finds anything on your topic that we have cataloged, not just books.  Use the filters in the left and right columns to sift and sort your results. 

Especially useful is the box on the upper right that presents the most frequent Subject categories used to classify the items.  The larger the type, the more frequently it appears in the hits. Click on any one and you will get all items classified under that category.