Not only great for file storage but they're great for moving. You can carry them well they stack well and they dismantle and fold up for the next time.
We have used these boxes previously (and currently) for moving. They work great sturdy enough for heavy books but the size helps keep the weight down so anyone can pick them up. The handles are a great help as well. Easy to put together.
I use it to store yearly files for archiving. These boxes fit file folders perfectly. Tip: Tape a ZIP LOCK bag to the box and insert a piece of paper labelling the contents in it rather than writing directly on the box. This allows for further recycling by simply swithcing the paper label!