The main subject is centred for sure and the photo would be more dynamic if he were slightly away from the middle. However, I would leave the man in the black T-shirt in and with either a 3X2 or 3x5 aspect intercept the woman wearing a yellow hat with the right-hand vertical thirds line. B&W works well and is not a bad idea since, as Lou mentioned, the distraction caused by colour in peripheral areas is eliminated; however, the books are a wonderful patchwork of colour themselves and I'd be inclined to stay with colour and live with the problem.
If you like I could post an example crop or two.