AOA
Look guys the choice of books is entirely yours. Dr. Khalil who secured 66 marks in pak affairs asked me to go for "Trek to Pakistan" by Ahmed Saeed. The book is fantastic.It extensively elaborates everything that happened from 1857 to 1947. I didnot find any question in previous papers beyond the purview of this book. And for post-partition i will strongly advocate for Military and Politics in Pakistan by Hasan Askari Rizvi. I went through this book after my exam but found that many of the post partition questions and objectives were asked from this book.
But the best approach for css prepration is to go for multiple books. The book you find most appropriate and suitable keeping in view previous papers and syllabus, make it your primary book. Your notes' 60% material should contain the arguments and facts and figuresof this primary book. Then go for other two to three books. Extract important qoutations and facts and include them into your notes. Paper checker should come to know that you have went through multiple books rather than relying on single book. This technique will fetch good marks.
Now i give you an example. I extracted a qoutation describing the plight of muslims after War of Independence from 'Emergence of Pakistan By Chaudhary M. ALi".
"too proud to co-operate with the victor,
too sullen to adjust themselves to new circumstances,
too embittered to think objectively,
too involved emotionally with the past to plan for the future,
Muslim society in the decades following the events of 1857 represented a picture of disolation and decay "
Look at the beauty of words. So what you need to do is to make a difference. In every subject, in every topic try hard to remember those things which common people forget. Go for uniqueness. It will help you alot. All the toppers have been unique in their approach.
Note: Never blindly follow suggestion of any person. Do your own analysis and if other person's arguments have weightage then go for it other wise leave it. Seek guidance from everyone but go for your own approach.

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Whatever mind can conceive,it can achieve - W.Clement Stone