Muslim Law is also one of opted subject of mine and truly speaking it is an easier and high scoring subject. I have appeared in CSS 2011 and went through this book

Islamic Jurisprudence and Muslim personal law by Dr Liaquat Ali Khan Niazi

indeed found a nice and informative book.

If you want to pass the paper go through this book but if you want to get high score then go through

D.F Mulla (Principles of Mohammedan Law and Jurisprudence by Abdur Raheem.
Outlines by Asaf A.A. Fayzee

Thanks

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Mitta do apni hasti ko, agar kuch martaba chahiye,
k dana khak men mil kar gul-i-gulzar banta hai.