Writing Books - Up, Down, Up, Down

@adamclark83 I think the issue might be your chair. I know this sounds weird, but there are some items that you need to lock into place, just placing them down isn't enough. For instance, with the chess table, there are only certain chairs that will lock on to the chess table. The desk you place a computer on is also an item that has specific chairs you need to use. Try using a computer chair, and and see if your sim can reach the laptop. If they can reach the item, they should sit and write. If you correctly lock the chair and desk together, there will be a green border around both items in build/buy mode. Once locked together, you should be able to move the two objects as one cohesive item. If you place a chair that does not lock into the desk, you'll move be able to move the items separately.

In the past when I put a laptop on the kitchen island/bar, my Sim couldn't reach it while sitting on a chair. If they can't reach it, they'll wave their hands no, an icon appears above their head indicating they can't reach it, and they'll ignore your command. With islands/bars, you can only use barstools, so they couldn't reach the item because the chair I used didn't lock onto the island/bar.

Anyways, try changing your chair to one that locks into the writing desk and see if that helps. Worse case scenario your sim just keeps going to the bookcase xD