What have you read of Engels? Socialism: Utopian and Scientific is one of my favorites. Other than some of his letters, forewords, and some essays, I’ve been really wanting to read The Conditions of the Working Class in England, since it’s referenced in Capital; and I think I have something else saved by him on my Kobo, can’t think of it ATM. I think Engels is really easy to grasp; Marx is a phenomenal writer but unless you’re in the mood to read about 1. Economics 2. Dense academic history or 3. A blistering criticism of some “Young Hegelian” scholar like Feuerbach or Bruno Bauer its hard to find something of his to just easy-read. The Manifesto is pretty accessible but it was mostly written by Engels, the two men were really one author most of the time, and I’ve read the manifesto several times and while its good its not my favorite work.
Sorry for coming off confrontational, but you picked two very good and influential thinkers to target. You could have said “don’t just read Malcolm Gladwell and Sam Harris” or “Jordan Peterson and Ben Shapiro,” who are all hacks, but very popular authors; whereas Marx and Engels have fallen out of fashion. It’s conspicuous, is all.