If they actually reset, then you probably have a hack conflicting with the action. Try taking out your Downloads folder (or at least the folder with the hacks in it) and check again. If it goes back to normal, you need to track down the hack that is causing this.
If they don't actually reset but they get the book, read for about a sim minute, then put the book down, this is an apartment life glitch. A lot of people have it. It's caused by the sim learning one of those special skills - learning physiology causes your sim to start learning at a really fast rate, learning any other special skill (not cooking, etc, but one of the "special" ones like fire safety or anger management) makes them stop learning unless it is night. Yes - they will study normally at night. Try patching AL and see if that helps. Or have your sims study after 7pm only
