The way it pops out makes it look a little bad I would ether tone it down or add a back to it also I think a top piece would help as well to make it feel more like a piece of furniture than some random pieces of wood. I would also go for a different color as right now the color looks like a poop brown a Darker Brown or a Badge color would look nicer. Also the edge piece is uneven with the rest of the model. Other than that its pretty decent design wise.
Not bad for him just getting started, I think that the shelf is so simple, yet it looks just like a shelf needs to be. If I am being honest, when I first started, I was really bad, and my shelf would have probably looked way worse.