Karen Legge, Linda Sherry, Sally Gadsdon and Philippe Harari   Psychology A2 for OCR Heinemann

Another book which covers all of the specialist choice options.  Again, like the book above this is a highly recommended text.  The 'key studies' are clearly summarised and evaluated and exam techniques are shared. 

 Fiona Lintern, Merv Stapleton and Lynne Williams  Study Guide for OCR Psychology: A2 Level Hodder and Stoughton

There is also a Psychology in Practice series from Hodder and Stoughton which consists of 6 books with each one covering a specialist choice option.  They are all pretty good.

This is not a book but is in fact interactive software called Understanding Correlation. It is designed to run on school or college networks.  It is very simple to follow and has interactive quizzes.   It is very highly recommended - but then I would say that wouldn't I?

Mark Holah Understanding Correlation.  
Can be ordered from www.learnbyit.com