This does sound interesting. I'm not familiar enough with either schizophrenia or modernism to comment on how true it is. I presume a psychiatrist has a good understanding of schizophrenia, at least!
It's one of the most fascinating books I've read! I'd recommend it just for the explanation of modernist art and its defining features. Correction, he's a clinical psychologist who works with phenomenological understandings of schizophrenia.
Schizophrenia is a really strange illness that basically has no consistent identifiable characteristics on the surface. The state is basically defined by its sheer strangeness and resistance to interpretation. He goes into all these underpinning psychological mechanics but the explanations are very vivid and full of poignant analogies.
Here's one patient describing her experience of the early stages of her schizophrenia, taken from her diary.
"For me, madness was definitely not a condition of illness; I did not blieve that I was Ill. It was rather a country, opposed to Reality, where reigned an implacable light, blinding, leaving no place for shadow; an immense space without boundary, limitless, flat; a mineral , lunar country, cold as the wastes of the North Pole. In this stretching emptiness, all in unchangeable, immoble, congealed, crystallized. Objects are stage trappings, placed here and there, geometric cubes without meaning. People turn weirdly about, they make gestures, movements without sense; they are phantoms whirling on an infinite plain, crushed by the pitiless electric light. And I - I am lost in it, isolated, cold, stripped, purposeless under the light. A wall of brass seperates me from everybody and everything... This was it; this was madness, the Enlightenments was the perception of Unreality. Madness was finding oneself permanently in an all-embracing Unreality. I called it The Land of Light because of the brilliant illumination, dazzling, astral, cold, and the state of extreme tension in which everything was, including myself."
This initial stage is characterized by the person having lost contact with things, or everything having undergone some subtle, all-encopassing change. Reality seems unreal. No hallucinations or delusions but everything just lacking human resonance, totally fragmented but at the same time vivid and illuminated with brilliant dazzling light, some experiencing a crystal clear profoundly penetrating vision of the essence of things, yet this meaning always seems just beyond of comprehension. Even the most articulate of patients describe an inadequacy of language to describe this all-pervasive mood. They feel no joy or sadness but either eerie anticipation or sometimes a kind of electric exaltation. A conjoint sense of meaningfulness and meaninglessness.
He talks about the paintings of proto-surrealist Giorgio De Chiciro here. Himself a schizoid person who used to describe his view reality as a museum of strangeness.