The 2nd volume of the correspondence between Marx and Engels, related to the writing and publication of Capital, includes letters covering the period from March 14, 1868, to June 28, 1895, almost a month before Engels' death.

The content of the letters from this period focuses on theoretical and practical issues that are directly or indirectly associated with the 2nd and 3rd volumes of Capital, which were published – after processing the relevant manuscripts of Marx – by Engels in 1885 and 1894, respectively.

Additionally, a significant part of the letters discusses the preparations, translation, and impact of the publications of the 1st volume of Capital outside Germany, specifically in Russia (1872), France (1872-1875), Italy (1886), and England (1887), as well as the editing of the next three German editions of the 1st volume.

Through the letters, the extremely difficult living, health, and working conditions under which Marx wrote Capital are highlighted, while at the same time, Engels' tremendous material and intellectual support is emphasized, without which this feat would not have reached the point it did.

After Marx's death, Engels transformed from a second violin – as he characterized himself – next to Marx into the first violin of international Marxism. In many of Engels' letters written after Marx's death, his agonizing effort to collect, classify, and process the enormous amount of manuscripts left behind by the "Black" is illuminated.

Engels had to make a series of decisions related to the utilization of the incomplete manuscripts left by Marx while also representing Marx in discussions regarding his theoretical economic work, safeguarding the essence of his thought, which had been formed in direct interaction with him.

The last part of the 2nd volume consists of an Appendix that includes some excerpts from Engels' successive wills, mainly related to the inheritance of the manuscripts (incomplete texts, letters, margin notes, etc.) both of himself and of Marx, which were in his possession at the time of his death.