Keep in mind one thing that you are opting psychology not to just pass it, but to increase your marks.As for as scoring trend of this subject is concerned,it has been a scoring subject even with the preparation of selective topics and using notes like material(sher bano's book).It is the only reason this book has been suggested by a number of forum members and Csps too.but now keeping in mind paper trend of CE2013,one can presume that paper pattren of coming exam will be even more conceptual and general and candidates of this subject can be tested in terms of knowledge and skills.
So most important thing now, is the selection of resources.i will suggest you to buy some standred books.Here is the summery of books recommende by majority of forum members;

1. understanding psychology by Feldmen
2. intro. to psychology by Richard & Morgan
3. psychology themes and prac. by Wyne Wieten
4. David mayers psychology

For paper two there are some other book as well.I have pesonaly bought first two of them and finding them very helpful.They cover each and every topic within the domain of syllabus.and if any topic is missed out, option of googling is always open.

Regards