Abstract Landscapes! - Nature Coloring Book Vol. 2 Grayscale Edition - Grayscale Coloring Books

If it's relaxation you seek, then here is your answer! Coloring gives you the time to sit back and not think about anything that's stressing you out. Instead, you can just focus on picking a color and filling the lines. Since it's abstract, you can choose, use and mix any color that you like! There's no limit to what you can do!