Marx was the first person who announced that politics is the superstructure of economical base. That is why he wrote many books on economy but that was not purely economics books that was political economy books.

His famous books on political economy are:

Comments on James Mill

Economic and Philosophical Manuscripts

The Poverty of Philosophy

Wage Labour and Capital

On the question of Free Trade

The production process of Capital

Theories of Surplus Value

Das Capital

These all the books are famous which is written by Marx. Marx has written many books on various topics but he is famous for Economics and Philosophy.