Once upon a time, I worked for a law firm that kept case documents in notebooks. Reusing the notebooks from one case to the next meant labeling and re-labeling the spines, and that meant sticky residue.
Sometimes there was leftover glue around the edges of new labels. Sometimes the old glue was so old that the new labels refused to adhere. Either way, replacing the labels without removing the original glue was highly unsatisfactory.
The managing partner of the firm was quite meticulous (a nice word for various other expressions that mean "excessively attentive to details"). I could see his point, of course: when you need a particular set of medical records ASAP, what you don't need is a selection of sticky notebooks with no labels.
That's how Goo Gone came into my life. Now instead of being the notebook custodian's secret weapon, it comes in handy for books and the occasional thrift store purchase.
I'm not a big fan of the stickers they put on book covers after the fact. If I'm planning to keep the book in my permanent library, I remove the sticker. Provided I do it carefully and don't make any creases, using Goo Gone means that after I'm finished, you can't even tell the sticker was there.
Because about 95% of my books are used, sometimes other people have done a poor job removing the various promo or pricing stickers. Like this.
And don't get me started on those nasty thrift store price tags that disintegrate into a jillion segments when you try to remove them, no matter how carefully.
So for all those uses, I heartily recommend Goo Gone, which is widely available and not nearly as well known as it should be. A bottle lasts a very long time and it has a nice orange scent, too.
A few drops, a momentary pause, a few swipes with a paper towel, and voila, the cover is as good as new.
Being a liquid, it only works on non-porous surfaces, but it's fine for a glossy dust jacket or the cover of a paperback. There might be a tiny sheen left behind from the citrus oil, but that disappears rapidly with a quick polish with a clean paper towel. (The faint stain here is from the sticker, I think, not from the product. I applied the Goo Gone over the entire word "of" and it wiped off without a trace.)
I keep my trusty bottle in a plastic bag, just in case of drips or leaks. Which have never happened, but seem like they might, someday when I forget to put the cap on tightly enough.
I know, I know. I'm pretty meticulous.