The clear lines, and shapes on the shirt is attracting attention along with the interesting expression on the face. keeping the eyes both the darkest and lightest point and on the third lines create it as the main area of interest and the shirt is a secondary point of interest the third is the sign on his back. This is a success.You could refine with detail the face a little more if you like. Bravo!
My Book is "The Art Advantage" sold on amazon.com if you would like to look inside the link is
http://www.amazon.com/Art-Advantage-Increase-Artistic-Intelligence/dp/1491227117/ref=sr_1_4?s=books&ie=UTF8&qid=1424959901&sr=1-4&keywords=%22The+Art+Advantage%22