I got five notebooks from Massdrop this week, just as I needed to start a new one.
The "1951" notebook is a revival of an older product, with a sort of composition book styling only more sophisticated. I like the monochrome cover with an overall fishnet-stocking pattern and a blank cartouche for a title. They're book-bound, with Clairfontaine's brilliant 90-gram paper. I have the A5 size, which I've come to like a lot.
The paper is wonderful: very smooth, substantial, with no bleed-through whatsover. I use slightly desaturated inks, so your experience may be different but it works a treat for me. It's right on the edge between absorbent and resistant, so I don't have to blot everything. i also like the purple color of the ruled sheets.
The cloth binding is very high-quality, but it prevents the notebook from lying flat, which is an inconvenience to a left-handed writer. Otherwise it's one of the best notebooks I've ever used, and I'm glad I have multiples.