You get what you pay for, and these shelves will fit in smallawkward spaces. Do note that they protrude from the wall quite a bit so make sure you have enough space. They definitely need to be anchored to the wall, but unfortunately the way to anchor them is complicated because there are two points to anchor, not one. So if your floors are not even, you’ll need to measure quite a bit to make it perfect. 
Ultimately, I will be returning because of the hassle and the mediocre quality.