part 1: Sohail Bhatti's, as it offers a lot of quotations which is everything in history exam and a comprehensive compilation of part-1's syllabus.

part 2: "Trek to Pakistan" by ahmed saeed, I'm not sure about author's last name, this book is underestimated very so often but it is a highly recommended reading. Quoting 39th common ASP, "give it a couple of times reading like reading a story book"
For part 2, I.H. Qureshi's is also a good option.

Now a serious piece of advice: Don't let yourself get baffled by a lot of options, CSS exam is not about how many books you have consulted or how better you have prepared your notes, in fact it is about delivery, and managing yourself. I have had sittings with couple of CSPs and they agree on one thing: It is better to read a single book twice then to read 2 books once.
And after all in a competitive exam it is simply not logical to aim for the perfect score, for instance, you don't need to look for 20/20 in objective part. hopefully you are getting the bigger picture of what I am trying to sketch here. And by the way one of my contacts scored 158/200 in indo-pak 2009 by the aid of Sohail Bhatti's and Trek to Pakistan.