Carrying thick sketchbooks in my bag usually strains my shoulders. And I find that I only use up 2-3 pages during an outing. So I started making my own A5 sketchbooks with less paper. They are small enough to put in my bag and also light. I also wanted good paper. So I would go to the paper suppliers and try to find the most suitable papers for drawing. Then I would staple bind them and put it through my trimming machine at home.
My latest sketchbook uses 200gsm yellow paper. It's called Vellum. This time, I wanted a paper that was smooth enough for pencils and also able to take watercolour washes. Take note that this is not watercolour paper so don't expect watercolour paper qualities. But it can take light washes as you can see if my drawings. The paper is also thick enough so it does not buckle much. The yellow paper also gives a nice overall warmer tone to your drawings.