When Karl Marx was actively writing Das Capital and the Communist Manifesto, he was living in London. He was a German who moved to London and saw first hand the opening stages of the industrial revolution.
He was a very smart man and his predictions were logical and sound. During his lifetime there were virtually no trade unions, child labour was rampant, and people would often die on the job with no compensation given to their family. A few very rich captains of industry(robber barons) ruled entire sectors of the economy with a monopoly. Therefore wages could be kept artificially low, and there was enough of a labour pool that unskilled workers could be replaced by desperate people moving to the cities from the countryside. (This is much like what is occurring in China in modern times.)
To be a poor cog in this economic machine (a proletariat) was very depressing and there was very little room for upward mobility in a very class oriented society.
With this sad social landscape it is no wonder why Marx theorized a social upheaval that would spread prosperity and equality among all workers. I empathize with anyone who shares this vision in theory. However, every time that Marxism(communism) has been implemented on a nation wide scale it has been an unmitigated disaster. The reason for this is that it creates a climate of stagnation, paranoia and uncertainty.
When all products are to be shared, it takes away the incentive to work hard in order to succeed. The ambitious are punished, and the lazy and corrupt are rewarded.
Here is a partial list of large scale communist states that failed dramatically. Russia(and most of Eastern Europe), Vietnam, Cuba, Venezuela, North Korea etc...
China is communist in name only. They have a controlled market, but they have embraced free trade and capitalism and they are now prospering.
I know that many people are very passionate about Marxism one way or the other, but the death toll caused in its name over the past century is truly staggering and terrible.