I wiped down this wood bookshelf with some wacom wood oil, so

i think you need wood finish if u want to keep it shiny

you don't. If you did it right, the film will harden, as the oil cures. If you did it wrong (ie, didn't wipe off the excess well enough)... well, you're fucked.

Look at the incredients, because I'm not familiar with that particular product, but I'd guess its probably boiled linseed oil with maybe a little solvent.

Was the wood finished before? Because if it had a film finish (poly, wax, shallac, etc) it isn't going to penetrate and will just turn into a sticky mess on the surface.

If the wood was unfinished, it will penetrate and cure into a good looking, but not very protective finish. You can top with any of the above finishes after it cures.

If you do something like this again, I'd recommend my favorite finish. 1/3 linseed/tung oil, 1/3 poly (glossiness of your choice), and 1/3 solvent. Mix in a jar and wipe on. You get the look of oil, and some of the durability of poly without the coated-in-plastic poly look.