Here is a list of useful reading materials:

Introductory book: Rich Christians In An Age Of Hunger by Ron J. Sider

Effective campaigning: Planning an effective campaign - The Strategic Process by Barbara Crowther (CAFOD campaigns)

Campaigning: The A-Z of public advocacy by Des Wilson with Leighton Andrews (Hawksmere press)

Trade Issues: No Logo by Naomi Klein Trade for Life by Mark Curtis (Christian Aid) Captive State by George Mombiot

International development: Does Aid Work? by Robert Carson (Clarendon Press)

Aid: rhetoric and reality by Teresa Hayter and Catharine Watson (Pluto Press)

General: You can Make a Difference by Tony Campolo The Sins' of the Fathers by Roger Mitchell and Brian Mills