It's a very simple mods for people who don't like killing cows.
There will now be 3 different materials you an use in addition to leather, when crafting books. That includes;
-Wood Planks
-Bamboo
-Sugar Cane
Obviously a book functions perfectly well when made from a wooden or bamboo cover. The sugar cane one is simply more for a QOL change, rather than realism, so that if you wish, a sugarcane farm can fully provide you book materials, both the cane itself, and the paper you'll need per book.