Another timesaving option is to forgo bookbinding completely by upcycling an old book as your base, such as in this altered book tutorial by Jane’s Apron. You can still paste or draw or pin on all the components that you want to use in your book, without the trouble of finding an appropriate cover or sewing in a sturdy binding.
On a personal note, I’ve always found that my altered books work best if I choose a very thick book to start with, then tear out half the pages before I begin. What with all the embellishments that I tend to add, this keeps my finished book from becoming so thick as to be unwieldy.
[Image by Jane’s Apron, used with attribution]