As an example I'm going to use my 20th Anniversary Edition of Harry Potter.
Things you need:
- Rubbing Alcohol
- Several Cotton Pads
- Your Book
Peel off as much of the sticker as you can, the less of the paper part of the sticker is left on your book the easier it will be to get off the gunk.
Soak your cotton pad in rubbing alcohol, but not too much that it's dripping, you want it to just be damp enough that it will soak into the remains of sticker. You don't want to get any alcohol on your pages.
Press the cotton pad to the mess of sticker and give it a moment to soak in a bit, then start rubbing away at the sticker.
Use a dry cotton pad to wipe away the rest of the rubbing alcohol and goop left over from the sticker.
If you didn't get rid of all the sticker the first time, then the rubbing alcohol will do that for you. There will be a bit of scraping necessary to get off the rest of the paper part of the sticker, but it won't damage the book. I promise, just as long as you don't use anything very sharp, just use your nail or the back of a knife. If there is still gunk left over just repeat steps 3 and 4 over until you're satisfied with it.
This process also works with getting sharpie off of your books. it works very quickly and easily.
I hope this helped some of you guys out, I know it changed my life when I stumbled across this knowledge.