The "pre-drilled holes" on the shelves are more like indented suggestions. I don't have power tools so I had to hammer the screws in partway in order to be able to actually put this together. Perhaps because of this suboptimal construction method (I'm not about to go to the trouble of trying to return it in the middle of a pandemic and I did need shelves), the finished unit leans forward in a decidedly unattractive way. The shelves are actually pretty stable and it's not wobbly, it's just rather ugly. If I could go back I would definitely purchase a different bookcase.