Simple, but pleasing...
I like how abstract art- utilizing certain elements and principles to produce something aesthetically pleasing.
The composition shows a sort of unity- in how the shapes reflect. The stark contrast is a nice choice as well. I think this wouldn't seem as effective if it had a vertical composition.
As a fan of fractals, I adore repetitious elements (the bold rectangles and lines). Even when the opposing values- it does express a likable sort of symmetry (also a fan of op art and illusions.)
I realize how simple it must have been to make this- but the arrangement makes it.