Updated Jan 2019
Here's the sketchbook that I used yesterday for the panorama sketch at Singapore River.
This is called the USKbook, aka Urban Sketch Book that's made by Sennelier>a?, the same company that makes the watercolour.
This is one of two USKbook formats. The black linen cover one is around A6 size while the other which has a green cover is A5 size.
It's a 4 by 6 inches accordion page sketchbook with 10 pages on one side, and 8 on the other. The length is slightly less than 100 cm, or 38 inches.
The cover is cloth-bound with some sort of design stamped onto it. It's small, lightweight, and easy to carry around.
The paper texture is smoother than fine grain cartridge drawing paper. This paper is not watercolour paper but it's 340gsm so it can work with washes. I will not put more than 3 layers on the surface though. 3 layers seems like the limit at which the paper surface will start to get mushy.
The paper is not cotton so certain watercolour techniques are not going to work well. More specifically, wet on wet techniques won't work well. The paper soaks up water easily and prevents the paint from moving around. This means it's difficult to create smooth colour transitions or gradations.
Downside of the sketchbook is the gutter. The paper surface breaks at the fold because the paper's too thick. So the inside of the paper, the part beneath the paper surface, can be seen.
When you apply watercolour, the watercolour will bleed through to the other side. Personally, I would not want to use both sides because if I use the other side, the watercolour will bleed through and affect the art on the other side.
The smooth surface works well for ink also. I tried gel pen and fountain pen. Lines appear sharp and there's no feathering.
Overall, I think it's a good and fun sketchbook to use. You can use it for panorama sketches or collage of many smaller sketches. The downside is the gutter where water or ink can bleed through. The sketchbook is best used only on one side, and that can make the sketchbook pricey to use.
Should you need higher quality paper, you should get the green cover USKbook which uses 100% cotton.
4 out of 5 stars.