This is one of my favorite adult coloring books because it's just line coloring, meaning there is nothing to "fill in" which makes this perfect for gel pens. I like the dark background because I don't have to stress about going outside the lines and I like that I don't have to fill anything in because it's always so time consuming. The pictures are just of animals and plant scenery. I really enjoy this coloring book A LOT and highly recommend it for gel pens particularly.
