This is going to seem like a roundabout way to fix this, but it may be impossible to get the pattern off of the sticker intact. To remove the sticker off the book, try heat like I do in the tape removal course. After you remove the sticker you could try lighter fluid to see if you could remove what was still stuck to the sticker. (Don't use heat and lighter fluid at the same time!)
All that said, I might approach this in a different way. Assume the pattern stuck to the sticker is a lost cause and instead, make a color photocopy of the pattern onto some Sekishu Japanese tissue. "Cut" to size and paste over the missing spot. Cut is in quotes, because you could use a pointy brush with water on the verso side to be able to tear the Sekishu. I have done this before to good effect. Cheers.