Well plz keep in mind that no one book is perfect for CSS as it does not contain all the detail which is being asked by FPSC. Nowadays very deep questions are being asked. Whenever you have time you must give to compulsory subjects as people mostly lag behind in those subjects.

I usually read Rabani's book alongwith INDOPAK History book of Ehsan-ullah Saqib (Dogar Publishers) which is comprehensive one.

When you read any topic, highlight important points that you think can be asked in MCQs. Then write them on simple pages topic wise and try to solve them after finishing topic. When you separate MCQs of each topic it will save your time for finding MCQs from here n there. and in last night of exam u can revise it quickly.
Sure, I'll send you MCQs which I have.