Diane Arbus created many of her portraits throughout NYC. Central park is where she created numerous. One particular place was Bethesda Fountain near the entrance at 72nd street.
Find Bethesda Fountain and the area where this couple was posed. Standing there look to your far left you’ll see a grassy hill. Once up there look for the one lone stone on the perimeter of grass and bushes. To the left of that stone you’ll find your disguised book in the bushes. Good luck and log your find here.