I have used various Khadi sketchbooks. Here’s the hardback one. It is about 8inches by 10 inches, 20cmx25cm.
The paper is soft and absorbent, a friendly surface. It’s not so easy to draw on with a fountain pen. The pen tends to pick up little bits of paper, and snag on the surface. But it’s great for watercolour.
Here is the soft back one (July 2019):
I prefer the “smooth” paper. This isn’t really smooth, it’s more like “cold-pressed”. It doesn’t snag the pen quite so much as the rough.
Here are pictures done in Khadi books.