Chance of slipping the nipple is not so good in the brackets, as it should be. If You Care with a rubber mallet strikes the skin from above and with a screwdriver or pliers presses the nipple inward so the nipple does not slip out even.
The only possibility for improvement that I see it, if you do not need all the floors, this could then build between two shelves and thus would almost three shelves would. Unfortunately that does not work, because the corners are angular and the transverse struts can be secured from the inside.
Property me now appointed with only 45 cm depth two shelves'm curious.