Having said that, it is a fascinating book. It is easily one of the most influential books of modern times, and has influenced history to an outstanding degree. Moreover, it provides a critical insight into the thought of Marxist socialism in particular and anti-capitalists generally.
Kapital is as much a political work as an economic one, as it examines the then-current economic system within the then-current politcal context.
As an economic work, I believe it fails early in putting forth a theory of commodity value whereby a commodity is said to be "worth" the amount of labor that went into it. In truth, there is no rational basis for that belief - he mistakes cost with value. But it is an easy mistake to make and is frequently made even today by those who, rightly or wrongly, see workers who they believe are unfairly compensated.
From that flawed premise, he builds a theory of capital accumulation and allocation which, though also flawed, will similarly appeal to many. Finally, he calls for state appropration of capital from capitalists.
As a political work, it discusses labor and enterprise within the context of class struggle, as he sees a labor class struggling under the oppression of a capitalist class. It is this struggle - countless seemingly powerless workers fighting to survive in a society politically dominated by a few wealthy industrialists - which I believe Marx was really trying to solve.
Marx saw a change to state-controlled socialism to be the answer, which is why he wrote Das Kapital. Other observers might have found an answer in religious revival or elsewhere.
Marx is not the first - nor the last - to have many of the ideas put forth in this book. But he has certainly become an icon for those ideas. Through Kapital, he has influenced the course of history and affected the lives of many millions. The book is worth a read. Just don't expect it to be pleasant.
For it inaugurated a new era in the relationship between men of all social conditions in the whole world and in years to come. It is the book where all the reasons for the downfall of capitalism in the end of the XIX century are pinpointed with a precise and polemical style, trademarks of the German author, and where, for the very first time in the story of History, historical movements are treated coherently as the necessary (deterministic) events of the social movements of humankind since the beginning of civilization, something called historical or dialectical determinism by the author, who borrowed and inverted many concepts from the German philosopher Hegel.
Notwhitdstanding the importance of the book to West and East culture, this is not an easy book to read, given the intricacy of the subjects treated and also its lenght. For me the most attractive feature of the book is the disdain Marx had for anyone who did not agree with him, unabashedly fighting against Political Economists and Historians of all ideological collors. Despite all the rabid polemic, what remains after almost 150 years of the publication of the first volume of Das Kapital is the collapse of the communist world and the strenght of Capitalism, who learned the lessons of survival better than its ideological counterpart.