Audible.com seems to have mainly critiques of socialism. Top 3 results are The Fatal Conceit - HayekSocialism - Von MisesSocialism Politically incorrect guide Only then are the do we get to supportive works Why Not Socialism - G. A. CohenSocialism: A Very Short Introduction - Michael Newman
A search for Karl Marx results in Karl Marx: A Nineteenth-Century Life UNABRIDGED By Jonathan Sperber Karl Marx: Das Kapital UNABRIDGED By David Ramsay Steele Wisdom of Karl Marx UNABRIDGED By The Wisdom Series Narrated By Rick AdamsonVarious versions of the Communist Manifesto