I would think that your book case already has some sort of finish on it. Thus you would have to strip/sand the existing finish for your stain to absorb into the wood. Also, for a more predictable coloring, I would sand it down first. I've tried to stain over another finish and it did not turn out as expected.
If it is a melamine finish already, there is probably nothing to strip down to, other than particle board. Staining probably won't have any effect, at least not the desired effect, since melamine isn't wood.