Originally Posted by Anum Zara

8 months are not short. They are more than enough if you do totally dedicated study in these 8 months. Now it is time to study at least 8-12 hours a day to get syllabus covered and to revise it at least twice.
I cannot ask you to follow any 1 specific book as one book is never enough for CSS. It can be a case with a single subject but not for all. I am listing down all books that I am consulting. By these you can get grip on subject.
Optional subjects:
For IL:
1- IL by S.K Kapoor & Tandon
2- IL by JWT for topics according to syllabus
3- Past papers

For US history:
1- US history by Majumdar
2- Sir Naveed Bhutto's notes
3- by JWT
4- Past papers
(I occasionally consult peoples history of US by Howard Zinn)
(1+2 most recommended)

Pashto is not my subject

IR
1- JWT
2- Joshua Goldstien (Most recommended)
3- Parkash Chander
4- Globalization of world's politics
5- Past papers

Public admin
It was my subject in CE-17. I have changed it and I do not recommend to take it as optional. The best book which I have come across yet is Dr. Sultan Khan's book 2017 edition. Also never consult internet for this subject. Questions were in Pakistan's scenario. Not much reliable data is available online. No notes are available. Style of asked questions has been dramatically changed in CE-17. Not a scoring subject after change of syllabus. If you really want to take it as optional buy new book of Dr. Sultan. Solve all past papers. Never go for JWT. It is not good at all. ( I recommend you to switch it with more scoring and safe options)

Compulsory subjects:
CA
1- Dawn
2- JWT magazine
3- CA by JWT (Waseem Riaz Khan)

PA
1- Pak affairs by JWT
2- Pakistan & world affairs by Shamshad Ahmed
3- For latest topics daily dawn
4-JWT magazine

Islamic Studies
I am attempting in Urdu
I am consulting two books
1- Islamic studies by Hafiz Kareemdad Chughatai (Most recommended)
2- Islami Nazria Hayat by Prof Khursheed

English Essay:
Self practice of latest topics+topics in past papers and get them checked by teacher

GS&A
1- Mian Shafique's book by JWT for general science
2- Add more info from internet on book
3- For ability portion check link shared by MrArsalanKhan (moderator) in relevant section

English precis & composition
1- I am following the book by Hafiz Kareem Dad. I have found it best.
2- Plus past papers