Okay, I did form some rules, but there can be loopholes. This a simple story for the characters and transformation, not the rules for the item. (By the way, I made these before I made the comic)
1. Each person can only have one page. Ripping that out or destroying it makes the change permanent.
2. For the change to be removed, the writing has to be removed. Crossing out or covering up does not work.
3. You can make adjustments to previous changes, but it has to be after the writing on the same line, but it can't contradict itself (or if it does, the change might be really weird). You can't cover up the writing with other writing.
I'm sure someone will come up with a loophole for him to change back, but the fact is he does not want to. Hope this helps a bit.
but burning just does the same as crossing it out, so you must also write on the next page to activate a new transformation, or something along those lines, all I know is magical items are pretty complex xD
I've looked there, all that i found there was stories like this one.... Although there was that one with a giant red eye in it but, something told me that it would be wise to Not touch it. Are there any more places that it might be?