I would recommend Rand's Philosophy: Who Needs It then Peikoff's Objectivism: The Philosophy of Ayn Rand. The Introduction to Objectivist Epistemology (ITOE) is good but is a bit technical and not everyone has the interest and motivation to read it. At the very least, if you can find it at a bookstore, read the intro because it does a good job of setting the historical context on why the theory of concepts is so important.

BTW, in some ways The Romantic Manifesto which you mentioned is more difficult than the ITOE.