Jonathan Kozol doesn't present a single, concise thesis statement in the way a typical academic paper might. Instead, his argument in *Illiterate America* (which is the book I believe you're referring to; there's no widely known work titled "The Human Cost of an Illiterate Society" by him) is woven throughout the text. His central argument, however, can be summarized as follows:
Illiteracy in America imposes a devastating and pervasive human cost, affecting not only individuals but also society as a whole, perpetuating cycles of poverty, inequality, and diminished civic participation.
This overarching argument isn't explicitly stated in one sentence but emerges from the accumulation of evidence and anecdotes he presents throughout the book. He develops his argument through chapters detailing the experiences of illiterate individuals, the systemic failures that contribute to illiteracy, and the broader societal implications. Therefore, you won't find a thesis statement at the beginning or end, but rather the core argument is revealed gradually as the book progresses.