That's awesome! There are many discussions on here throughout the years about old tickets. Yes, there used to be a ticket system. My first visit in 1978 or so used these (I was seven at the time so I might be off a year or so). In fact, that's where the idea of "E ticket" rides being the best originated. Once you were out of tickets, you could buy more. Or you could do the free rides like "If you had wings" which used the current Buzz Lightyear track system.
There is an awesome thread on the Theme Parks Community Board titled "Pictures of things no longer at Disney World". It is an awesome thread of hundreds and hundreds of pictures.
I think your ticket book is an awesome keepsake!