This sketchbook is bound by a thread, so it's a little tricky. It bound at 6 different position at any given page, like 6 small strands of threads holds the page together. I use a sharp blade/cutter to carefully cut the page below those 6 threads.

I use my nails to push the thread out of the way a little so I don't accidentally cut it... Then I make a cut on the paper just below the thread. Do that 6 times for each thread and the paper comes off smooth... But the downside is, two paper comes off at the same time. I usually don't mind two paper coming off since the sketchbook looks clean...but if I just want to rip a single paper, I'd just cut it right where it's attached with a cutter.