The Australian-based Centre for Clinical Interventions has a consumer section with readings and workbooks on a number of disorders - depression, social anxiety, etc.
Not a bargain in the sense that it is not discounted as these seem to be free in general, but it is nevertheless free and it covers the same topics as many paid-for-books.
The resources come with the standard disclaimer that they are not a substitute for a personal treatment by a qualified professional.
The links to the PDF files can be found here:
http://www.cci.health.wa.gov.au/resources/consumers.cfm