Had so much fun doing these (mostly in French classes when I was bored). In the middle of the sketchbook I took a Udemy course for drawing, and it actually helped me improve a lot.
I learned just how much there is to art theory – from the line, to the shapes and forms you create. The space and depth you create on your canvas, how contrast and values are extremely important, the compositions, creating realistic textures and overall harmony and balance in your work.
The progress is quite visible between the first and last sketches.