Maruman Mnemosyne Grid Notebook- Horizontal A5 Layout, 5.83" x 8.27", 70 Sheets / 140 Pages, 5mm Graph Paper Journal, Perforated Pages & Wire-Bound to Lay Flat, Black, Made in Japan

I like this notebook - I get that linked one specifically with square grid on one side and blank page on the other. It’s really thin and low profile at that size but they have lots of other sizes and styles too. One of the few notebooks I’ve actually filled up and had to re-order because I used it all lol. I also like that the pages rip out. Only thing that would improve it would be a little pocket page in the front or back.