For the sections dealing with the neurologists, psychiatrists, psychoanalysts and "alienists" who populate psychiatric history, providing context primarily means showing each school's ideas and methods growing out of, or in reaction to, those ideas that came before. What this means, as Appignanesi makes clear, is that the history of psychology and psychiatry is somewhat cyclical, oscillating back and forth between opposite poles of thinking. The particular dichotomy with which Appignanesi most concerns herself is that between psychodynamic and biological psychiatry. Both camps are represented in every time period, but their respective popularity and standing wax and wane.
Appignanesi herself seems to favor the psychodynamic view; she thinks the current mania for brain imaging and tinkering with neurotransmitters loses sight of the fact that physical indicators (like unusual patterns of electrical activity or an excess or shortage of a particular neurotransmitter) can as easily be effects as causes.
To assume that sadness, even in its malignant form, is caused by a chemical imbalance may not be an altogether useful hypothesis or a particularly true one. I feel sad when my dog dies. That causes a change in my brain. The emotion isn't caused by the brain. Everything animate beings do or feel --- from watching a football match, to kissing, to eating --- causes complicated chemical change. But no amount of serotonin will bring Mr. Darcy to the door, make England win the World Cup, bring peace to warring neighbours or end global warming.
She thinks a mental-health system that focuses primarily (or only) on medication overlooks the beneficial elements of talk therapy, like personal growth, time away from unhealthy circumstances or relationships, having an outlet for problematic thoughts or feelings, and just plain human interaction.
She also draws a curious parallel between what she calls a culture of "cosmetic psychopharmacology" and the world of illicit street drugs. Both, she says, reduce human experience to a series of chemical reactions that can be adjusted for maximum enjoyment. She gives examples where the line between recreational and therapeutic drug use becomes blurred: high-achieving professionals (or students) using stimulants to boost performance, or research into adapting club drugs, like ketamine or MDMA to clinical use. She also points out that the same needs could drive a person to seek out either option for relief.
Apart from those few provocative arguments, which she confines mostly to the Introduction and Epilogue (though she does have a chapter on "Drugs," into which a lot of her criticisms of psychopharmacology diffuse), the rest of the book is primarily a series of biographical vignettes framed in neutral exposition. The most colorful scenes are taken from the lives of the literary and historical personalities who sought help from the mental-health professionals of their time, with Zelda Fitzgerald, Virginia Woolf, Sylvia Plath, Marilyn Monroe, Alice James, Sabina Spielrein and Théroigne de Méricourt among the most famous.
She uses the details from these case studies to make her second major point, which is that the nature of mental illness changes along with the cultural milieu from which it arises. For me, probably the most persuasive form of this argument is that the life experiences that can catalyze a psychiatric breakdown tend to be those that are most culturally fraught. In the uptight Victorian Age, when Freud was working, the sex life was inherently problematic, especially for women. Consequently, Freud found himself swamped with young women (and men) complaining of disturbing sexual fantasies. Today, it's not sex so much as food and the body that come with cultural baggage. Accordingly, we see a lot of eating disorders in young women, and less extreme forms of eating-disordered behavior (obsessive calorie counting, making categories of "good" and "bad" foods, guilt over eating "badly") in almost every woman.
Even if you vehemently disagree with these premises (indeed, I am not willing to go as far as she does in her agnosticism toward biological psychiatry), I would still recommend reading this book. It offers a wealth of detail about each era's reigning psychiatric theory and practice, and the case histories make for compelling reading. One of the things I liked most about her selection of biographical sketches was the wide diversity of outcomes: regardless of when they were treated, and under which orthodoxy, some patients got better, some were completely cured, some learned to cope sufficiently that they went on to live full and happy lives, while others killed themselves or remained in institutions their whole lives.