I bought a new sketchbook last week. It’s not filled with paper; the description on the back explains it “is made up of 80% calcium carbonate and 20% non-toxic resins.” The pages have a feeling similar to vellum, but extremely smooth. I tested in the shop with some markers, and they were very painterly on it, so I picked one up.
The odd thing I’ve found through drawing on this surface, though, is that the markers seemed to create a kind of finish that sadly was immune to the fine-line markers that I like to go back in with for detail. It clogged up two of them in short order, so I resorted to going back in with a mechanical pencil. It requires more experimentation, but I do like the kind of watercolor look that these brush markers achieve on the slick surface. Also the pages are slightly translucent, which is interesting.