Professor Claridge's last book on schizotypy was published in 1997, just as I was writing up my doctoral thesis, and it became a trusted companion for a good few months. This timely ‘kind of sequel’ does not disappoint.

Claridge & Mason have assembled 20 contributors from three continents, many of them eminent schizotypy researchers, to deliver an up-to-date critique of the topic. In the introduction they directly address the contentious issue of wheter schizotypy is a mild form of psychotic illness, qualitatively different from non-schizotypy (the quasi-dimensional model), or the extreme of a continuum of personality traits normally distributed in the general population (the fully dimensional model). The former is often called the ‘medical model’, and maybe I have just been lucky but all the psychiatrists I have worked with have been very happy to embrace fully dimensional models. Claridge & Mason do not dwell on this controversy – all parties are interested in psychotic-like phenomena after all. They deliver a well-balanced review of the field, arranged around the themes of measurement, biological basis, environmental factors and outcomes.

The chapter on measurement addresses definitions of schizotypy, including different dimensions (e.g. positive, negative, and the notoriously difficult to measure disorganisation). The summary tables of various measurement tools are very useful. The two sections on biology and environment are pleasingly respectful of the multifactorial nature of schizotypy, with each happy to accept and incorporate the important interacting role of the other. Methodological problems are not hidden away but highlighted throughout; the discussion of the difficulties associated with studying childhood trauma in relation to schizotypy is a good example. A minor criticism is that the chapter on inducing psychotic-like experiences does not seem well integrated into the rest of the book and the implications are not clear, but it is nonetheless a fascinating read. Who would not want to know about shamanic sweat lodge ceremonies?

I reached the end of Part II thinking that this is obviously a wonderful book to recommend to schizotypy/schizophrenia researchers, but struggling to see that it would feel especially relevant to clinicians. Then I read Part III, and I changed my mind. I think all clinicians would benefit from reading these excellent chapters. They are concise, well-written overviews of the value of dimensional approaches in clinical practice, the relationship between schizotypy and psychopathology, and the link between schizotypy and creativity. The principles are discussed critically and can be applied to all aspects of psychiatry.

The book ends with characteristically wise advice from Professor Claridge: high-quality longitudinal studies of high schizotypes are desperately needed to address tricky issues of causality and to understand the mechanisms by which schizotypal traits become psychiatric symptoms. He also reminds us that we should seriously consider the overlap between schizophrenia and bipolar spectra.