Cleaning Jello Off Textbooks

That sounds like a good idea, trying to keep books as nice as possible.

I would dampen a soft rag and gently rub it but not so much that you peel the paper.
Then I might dab some bleach on it and quickly blot it. When it was a clean as I could get it. I would iron the pages flat.

I did this with a library book that had some tea spilled on it. I went thru the pages and blotted them as dry as possbile. Then I shut the book and put bricks on it to flatten the pages for about 20 minutes. I flipped thru the pages and dabbed with a tissue. When dry, I dabbed them with bleach and then ironed them.