Bales finds two broad types of slavery.
Slaves are cheap, even disposable, and drawn from the poor, vulnerable, and dispossessed rather than from particular racial or ethnic groups. These are of course ideal types and modern slavery mixes elements of both, varying in its forms both between regions and across individuals. In each case Bales presents the personal stories of a few individuals, analyses the economic and political causes of their slavery, and sketches its broader social and historical contexts. Bales avoids sensationalism and takes care with his analysis. Common to all forms of slavery is the use of violence, overt or implicit.