For a limited period the British Psychological Society is allowing free downloads to members and non-members during the month of July of the Understanding Bipolar Disorder report . You will have to register with the site but the report is free once you have done so.
The report provides an overview of the current state of knowledge about why some people tend to experience periods of extreme mood and what can help. Much has been written about the biological aspects of bipolar disorders: this report aims to redress the balance by concentrating on the psychological aspects, both in terms of how we understand the problems and also approaches to help and treatment. We hope this report will influence the way in which services are delivered, so that more people have access to psychological treatments and that services will no longer insist that users accept one particular view of their problem.
Source: British Psychological Society