I think the final product turned out well, I didn't get the dimensions perfect because the books don't slide all the way in but it should still work.
In this unit I learned to main things one being a refresher on how to use a 3d printer and the other is that you should give a little extra room for error. It was good to use the 3d printer again but I think I really learned how to dimension things properly. If I would have given the slots one or to more millimetres of space the books would have fit perfectly. Next time I will take this into consideration when making anything.