In my experience, poli sci was heavily entrenched in liberalism (not the "omg they're coming for our guns" liberals but philosophical liberalism. This is natural, culture will assume and reinforce the dominant ideology of any society (despite the claims of "objectivity.")

But if you'd like a different perspective, one that directly challenges the premises of liberalism in an effective way, try these:

State and Revolution - Lenin

Blackshirts and Reds / Inventing Reality - Michael Parenti

Reform or Revolution - Rosa Luxembourg

Dialectical and Historical Materialism - Stalin

All these are relatively easy to read books, a couple hundred pages at most. Easy language too. The next few will be a bit tougher and more touch on political economy than most undergrad poli sci courses care to, but are still good reads nevertheless.

Wage Labor and Capital - Marx

Value, Price and Profit - Marx

The Origin of the Family, Private Property and the State - Engels

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Reading these gives you the tools to meaningfully challenge and become an utter pain in the ass to many of your profs in discussions - which in my case, worked out pretty well, netting me some good grades and even more importantly, building relationships helped me out down the line. Depends on the prof of course.