What are the themes of Newjack: Guarding Sing Sing?

One of themes of Newjack is the way in which the prison system degrades everyone in it, guards and inmates alike. At the beginning of the book, the author asks, "Were guards normal men who became violent once enmeshed in the system?" (page 19). He finds, by becoming a guard himself, that there are pressures on both guards and prisoners that make them locked in a cycle of violence. 
In addition, the author writes about the growth of incarceration. For example, when he wrote the book (in 2000), black men in California were five times as likely to be locked up as to attend a state university (page 19). As a result, there is a growth of the so-called prison culture even outside the walls of prisons.
Another theme is the pervasiveness of racism that affects both prisoners and guards. Black men are incarcerated at much higher rates than whites. In addition, African American guards at Sing Sing are accused by African American prisoners of being coopted into the racist system, even though many guards feel like they are just trying to do what's right. In addition, African American and Latino guards are tested in many ways. For example, they often recognized an inmate from their neighorboods. 

The themes of Ted Conover's nonfiction account of the months he spent as a corrections officer in New York State's Sing Sing prison, Newjack: Guarding Sing Sing, include:
The dehumanizing nature of the American penal system: Conover's observations of life inside Sing Sing prison are scathing. For prisoners and guards alike, the environment inside prison is unremittingly bleak. For the prisoners, crammed into small confined spaces with few amenities, no privacy, bad food, and the constant threat of being victimized by other inmates, the daily struggle to survive with even a shred of dignity presents an almost insurmountable challenge. For the guards, the constant threat of being assaulted by criminals with little or nothing to lose (except for confinement in solitary cells as a form of punishment), the low pay and the constant strain from having to police an overcrowded maximum security prison built over one hundred years ago is exceptionally exhausting. In the end, neither guards nor inmates come away from the experience better off.
The excessive reliance on incarceration as a form of punishment: One of Conover's themes is the abuse of the penal system—an abuse that results in the aforementioned overcrowding of prisons—as a means of punishing those who violate laws, especially drug laws. Mandatory sentencing laws for drug crimes are counterproductive and financially costly for a public whose tax dollars pay to incarcerate individuals who would be better left to treatment programs and to penalties that do not require incarceration under dehumanizing conditions.
The first of these two themes is the most important. Conover's perspective, not just as a corrections officer but as a corrections officer with a journalistic background and intent to report, provides for a level of critical analysis not otherwise generally available to the public. The "us versus them" atmosphere in which corrections officers and prisoners exist on a constant basis is draining on both sides and invariably results in some of the more surrealistic experiences Conover witnesses, such as the refusal of some prisoners to submit to mandatory body searches despite the certainty that they will be subjected to such invasive procedures by force if necessary. The point, Conover states, is that the only way inmates can protest excessive or absurd rules is to resist them in any way they can. This is simply a means of retaining some slight measure of individuality and maybe even dignity.