I’ve come across the word 回数券 in my WaniKani lessons, which translates to Book Of Tickets. I’m not a native English speaker so I occasionally stumble upon English words or phrases which I don’t know. When it happens, I usually just consult a dictionary or Google the words. However, with book of tickets I’ve found nothing, so…
If you buy a bunch of tickets, one way they could be distributed is by binding them together like a little book. Nowadays it’s probably more likely that a 回数券 will just come as one ticket you can use multiple times, but you might still get a small bound set of tickets in some circumstances.