I have used Pledge to take adhesive off of glass. Wonder if it would work on an iBook? Don't think there's anything in Pledge that would hurt the finish.
There is a product called Motsenbocker's that is made for adhesive removal. They make three different spray formulas to take different substances out of clothing. One is for proteins (blood, food--in a green-labeled bottle), one is for graffiti removal (pen, ink, markers--in a blue-labeled bottle), and one is for grease and adhesive removal (in a red-labeled bottle). You can find it in hardware, home improvement, or office supply stores. It's pricey, but very effective. Sometimes the red-labeled bottle is so effective that the drips from the spray remove its own label!