If you need a digital copy, you do not need to resort to piracy. Here are ethical alternatives for Our Political System by Subhash Kashyap :

While many websites offer "Our Political System by Subhash Kashyap PDF free download," it is important to consider the benefits of a physical copy. A hard copy allows for easier highlighting, margin notes, and quick referencing during revision. If you are looking for digital versions for the UPSC:

: Forms, types, and the system as established by the Constitution. Government Organs : The Executive, Parliament, and State Legislatures. Judiciary & Federalism

While Our Political System by Dr. Subhash C. Kashyap is a respected resource for UPSC preparation, it is often considered a "concept-builder" rather than a standalone textbook like M. Laxmikanth.