So you buy a nice two shelf bookcase but it’s wobbly and you know it won’t hold much. I’ve recently gotten one and my solution was to put L-brackets on it. After installing about 8 of these brackets at the cojoining parts of the shelving, it is now completely stable and ready for use.
Also, make it a habit to wipe down your shower walls after a shower. This prevents gunk build up and mold. It will be harder if you don’t clean it regularly.