I haven't read any of Sowell's books, but have followed his newspaper columns with great interest. The Left tiptoes around him like they do around Alan Keyes.
You MUST read his books. The columns don't come close to the depth of argument he presents in the longer format. In fact, I've stopped reading his short columns, they just don't measure up to his books.
In addition to the book previously recommended, also try The Vision of the Annointed.