Was Lincoln really into Marx?

There's no credible evidence that Lincoln ever read anything of length by Marx, or that he even knew who Marx was. Lincoln did read economics works regularly, but tended to favour mercantilist/protectionist works from Americans (that's also how he knew Horace Greeley, as a protectionist and journalist heir to Hezekiah Niles, not as the guy who gave Marx part time income to write up anonymous columns as a foreign correspondent).

The much-discussed "correspondence" between Karl Marx and Abraham Lincoln was not even sent under Marx's name, or addressed to him in return.

The 1864 letter, consisting of a resolution from the International Workingmen's Association to congratulate Lincoln on his reelection, was delivered under the pen of W. Randal Cremer, an abolitionist and trade unionist who generally rejected the violent revolutionary faction of the organisation associated with Marx.

Lincoln's "response" was actually a diplomatic courtesy note written and sent by Charles Francis Adams, the U.S. Minister to Britain. State Department records indicate that Adams addressed the response to Cremer rather than Marx.

So basically there's no evidence that Lincoln even saw the Workingmen's Association letter. And if he did, he had no idea it came from Marx because it carried the name of Cremer and the only official response to it went back to Cremer.

Here's a copy of the response letter with addressee in official US state department records.

In related news, Marxists like to lie about their connection to significant historical events in order to inflate their stature.