Nickel and Dimed is Barbara Ehrenreich's 1996 experiment of pretending to be a poor person and trying to subsist on entry-level jobs. While her study was not scientific and contained several assumptive errors (working backwards from a conclusion being the biggest) her account is a deeply personal one, and very informative about both her own attitudes and about working conditions at the time of writing (the book is about sixteen years out-of-date).
Many articles and books about poverty take a scientific, detached approach, heavy on statistics, but since Ehrenreich performed the experiment herself, she wrote the book as a first-person narrative. This gives the reader a better emotional connection to the story and the people she meets; instead of listing numbers and facts, she goes into detail about the conditions her colleagues live in, and how they are dealing with the stress and difficulties of living on minimum wage. A more dispassionate approach would leave the reader bored. By singling out and humanizing the people in her story, she allows the reader to understand and sympathize with them in a way that cannot be matched by statistics; people tend to ignore numbers because they cannot relate to them.
Ehrenreich's active, personal voice is therefore vital to the success of the book. Since it is almost entirely the subjective experience of one person, the book must be engaging to read or its message will be lost.