Ah! So WD-40 does the trick!
For years I tried to remove the huge ugly patch of sticker residue on the back of my white-covered copy of Philip K Dick's Man in the High Castle, and nothing worked. I don't know where I read about it. Perhaps on a forum somewhere but I admit I was skeptical.
I ain't now! No more stubborn sticky stuff! Bonus - it cleaned the book too. The only drawback is that the book smells weird now. I'm wondering whether I should spray Febreze on it now too.
Just remembered... the stickers on the books from the Times Warehouse sales have the most stubborn sticker residue. Right, time to hit the library with a can of WD-40.