There is no getting around it, this book is a little dark. Especially if the reader doesn't already know about the world of depression. Those who have lived with extreme anxiety or depression likely resonate with Wurtzel's point of view, though, and that's why such a dark book must be written. As she notes in the ending of her story, the introduction of better mental health medicine made it less taboo to talk openly about mental health, and by talking about her own mental health, she accomplishes that same goal—to de-stigmatize depression and anxiety.
The unseen battle leaves Wurtzel constantly afflicted and paranoid, and the depression amplifies the negative emotions she naturally experiences in life—the stress of school, work, moving, career, identity. Although these are all universal to the human experience, she experiences them with the full weight of her agony. When she interprets reality, she does it through a lens that was shaped by the trauma and horror of her family's divorce.
Ultimately, that's why the book is so important; it reflects two essential aspects of mental health and the public sphere: Firstly, it is another piece of evidence that those who suffer from unseen mental health obstacles, they don't suffer alone. By honestly explaining her life, Wurtzel offers company to those who maybe think they're alone. Secondly, she heralds the de-stigmatization of depression, having learned from the Prozac craze that when people talk openly about mental health, they tend to feel more hopeful and less alone. That, combined with good therapy and medication has put her on a more peaceful track.