Well imagine you open the crafting table interface. Put more than one (actually only tested with 2 and 8) written books in the middle slot and place book and quill items around (again: I tested it twice: first 3 books on the right site and an additional one in the top middle slot and second 8 books all around). Take the result and in the crafting grid will remain an itemstack with a red 0. In your inventory you can find all the copies but one original is missing! Hope it's clear what I did.
By the way as I said in the text I only tried 2 combinations (there are a lot more) but I imagine it's the same with all the others.
MC-78125
Written book gets lost in crafting table
Resolved
Duplicate
0
Don't use two books? Seems that 4>2, so if 1 written book makes 1 copied book, 2 written books - 4 Book and Quill = -2 Written Books, thus making 0? This is a bug, able to reproduce, my recommendation now is to not use multiple of them written books.