The memoir explores addiction both through the account of Nic’s struggles and through Sheff’s research, interviews with experts, and attendance of educational sessions at Nic’s rehabs. One of the most notable aspects of Nic’s addiction is the degree to which it changes him, both mentally and physically. The first time Sheff sees Nic after a meth binge, he is horrified to realize that his once vibrant and athletic son is now a shell of his former self (118). As the need for drugs drives all other concerns from his mind, Nic loses interest in his previous pastimes, quitting teams and responsibilities, and becomes “increasingly furtive, argumentative, and reckless” (105). He also makes choices that he would never previously have considered, repeatedly lying, breaking into houses, and stealing from his family. It is not long before Sheff looks at him and sees “a stranger. And yet he is a stranger whose every part I know intimately” (144). 

The book also highlights the insidious ways in which addiction works, particularly the power of denial. After observing that Nic “‘has a dangerous attitude—he doesn’t understand that he’s in trouble’” (145), a rehab counselor explains that “‘[h]e’s in denial. It’s typical of addicts, who maintain and believe that everything is all right, they can stop when they want, everyone else has a problem but not them’” (145).