Brother i don't think politics is a thing worth learning or studying, It is just an ordinary thing, the people at the tea shops are discussing Pakistani Politics..Not everything is worth learning, one must be perspicacious to know what is worth learning and what is not...It will help you neither in your CSS exam nor in anything else..If you want to make a good understanding of Politics then your nearest Tea shop or "Chaye ka Hotel" is the best place to make your understanding of politics better.

However, if you want to understand "Political Science" then i can recommend you following good books.

• History of Philosophy by Fredrick Copleston (Rome and Greece), it will help you to go to the beginning of Political Philosophy from the time of Plato and Greek city states, first democracies of the world)
  
• Western Political Thought by Judd Harmon
  
• Muslim Political Thought by Rosenthal

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Ever has it been that love knows not its own depth until the hour of separation.
But when love is one sided, holding off is no more an option.