Why won't my sim sit still?

That's the difference between 3 and 4. In 3, they read that book until you canceled it, or they became so miserable they just couldn't continue reading. In 4, they have all the other distractions, and they will absolutely try to do as much as they can at the same time. Including taking a quick meal or drink when doing business in the bathroom.

Its one thing I miss with skill books. That the sims kept reading them until you wanted them to stop.