How deep should a bookcase be? Pull the shelf out and see

A bookcase takes a strip of floor as deep as it is. Most books need far less than the shelf they sit on, so a slimmer case can give a small room its walkway back.

Slide the depth, set your wall-to-wall width and pick what you want to store: the plan shows how much walkway is left, and which items would stick out. Measure first, then fix any tall case to the wall.