Adding a hutch to an office desk is a good way to gain shelving space without losing floor space or having to install shelves. However you must consider that the hutch may look out of place if it does not match the color and style of the existing desk. Also, you must make sure the hutch is the right size so that it fits properly on top of the desk. Whether this is worth the trouble is up to you. In some cases, buying an entirely new desk that already has a hutch is actually cheaper.
Office desk hutch:
Office desk hutch pictured: Laminate Hutch with Doors Finish: Mahogany, Size: 71″ Wide by Regency. Sold by Wayfair.
Also of interest: Mmf Industries 2061DOBK Desk Organizer w/Dividers, 47-1/4 in.x9-1/2 in.x18-3/8 in., Black / Northfield Collection Credenza Hutch by Bush Furniture