Although i have read many books over the years for pak affairs yet i think it is the technique of answering questions which rewards candidates.
For history portion i revise pak affairs by imtiaz shahid.
For cureent affairs portion i always consult jwt.

I always start with introduction then main body ( reasons,impacts, remedies; whatever is being asked in paper ) and then conclusion. Answer should be analytical based; prove your point with facts ,figures or comments.