I really love the concept of this game, I did struggle to put the books on the shelf I did end up having to give up D: But I will try again! :)
Sorry to hear! :( I'm still confused as to why they are so hard to put into place, they use the same logic as other drag and drop materials. We considered removing it from the game but figured that with a little bit of trial and error our tester managed to do it, so in favor of having more content we left it in with the warning. But we agree it should be better.