This double pack includes Artsy Optical Illusions Coloring Book Volume 3 and Artsy Optical Illusions Coloring Book Volume 4. So, that means that you get all of the optical illusion illustrations from each of those volumes all in one coloring book. With 60 mind-bending optical illusions, colorists of all ages will delight in adding their own touch of color to each of the illustrations found in this coloring book. So, gather together your favorite art supplies and get ready for hours of fun as you color each of these beautifully artsy optical illusions. The back of each coloring page has been left blank. That makes these illustrations perfect for displaying after you've finished coloring them in.