Saturday with Mister-- Should I Laugh or Cry?

So the other day I posted all about cleaning my kids' bookcase out, right?

Well, after all that work, THIS is what Mister did the next day... and the next.....  more than once.....

Doesn't he look pleased with himself?

I'm not sure if I should laugh or cry....  On the one hand, he LOVES books.  On the other, I have to clean it up!

Sigh.

At what age does it become feasible for the child to replace books on a shelf vertically?  Boo still has a hard time with it too....  Though she's better about not throwing them all over the floor...