The first of the was Eleven Theses of Feuerbach. He is dismissive of Feuerbach for thinking abstractly, whereas reality is only concrete. I know nothing of Feuerbach, so can't comment, beyond the point of noting that the man who has the grandest of all unifying abstract "sciences" should find fault with someone for talking abstractly.
The second is Wage Labour and Capital. This work was originally by Marx and brought into an updated edition by Engels. There is much that corresponds simplistically with economic views of supply and demand. Marx seems to be making the case for a "living wage", since the fact that a wage can be insufficient for a family to survive is highlighted. Engels adds a preface to this edition because it was produced after Marx's death from previous articles. In this preface, Engels explains that the point to be noted is that, whereas the fair price should go to the value of the labor (errr, labor power) + the inputs, there always seems to be a markup, which is related to the corruption of the Bourgeoisie. Marx notes that the markup can be negative as well as positive, so it isn't clear to me that Engels and Marx are on the same page. This work was originally a series of articles published in the Rheinische Zeitung, which was closed by the government before the series was completed, so we really aren't in an easy position to say what Marx's aim was.
I haven't been keeping score, but will note that Marx, along with Burke and Paine who I have read recently, all use "Jew" as an insult. Or so I have heard each one of them do this at least once.