Latex paints, particularly gloss and semi-glosses have poor print resistance. 

They dry soft, and anything that presses against the paint leaves an impression.

This is particularly problematic for bookcases.

I painted my cases with an interior acrylic latex semi-gloss to match my wall color.  As it is, it would have very poor print resistance…  but it can be helped.

I top-coated my paint job with 3 coats, sanding between coats, of Minwax Polycrylic, which dries to a clear, hard, print resistant finish.

If you are painting a bookcase, and want to avoid fusing with final coats of polycrylic , a good alternative would be Kelly Moore’s DuraPoxy paint which also dries to a hard, print resistant finish.