I think the list can get very long very quickly. Yours is a good one. Engels can be easier to read than Marx and Socialism: Utopian and Scientific is great because it’s short and as liberalism hasn’t moved much in the 100+ years interim, it’s still highly relevant even if the names have changed. Then Parenti is Parenti, what more is there to say, and Losurdo is top notch, too, although I haven’t finished his book on liberalism yet.