Originally Posted by Sarmad 2

Hamid Khan's "Constitutional and Political History of Pakistan" is an outstanding book and covers most of the topics as stated above by Sheihryar Asif.

However, there are two more suggestions I would like to add:
1. Pakistan at the Crosscurrent of History by Lawrence Ziring
2. The Military and Politics in Pakistan (1947-97) by Hasan Askari Rizvi

Though they are no replacement to Hamid Khan's book, the first is useful as a brief introduction to politics and military in Pakistan up to 2004 (I think), and the second one analyses in depth the civil-military relations and politics up to 1997.
Ziring's book is also recommended if you need something written in a relatively informal and light manner to get you started. It will not be enough on its own though.