Edge Banding
Before applying a finish to a bookcase or shelf project made from plywood or other sheet goods, you have to decide what to do with the exposed edges. They're normally rough, and with plywood, the visible plies detract from the project's appearance.
For a plywood project that you plan to paint, fill and sand any exposed edges. When working with melamine-coated medium-density fiberboard (MDF), use preglued melamine edge banding. It's available in almond or white. Simply cut it to length and iron it in place.
For a bookcase or shelf made from furniture-quality hardwood plywood, cut and attach molding or thin strips of solid wood. A quicker method is to apply wood-veneer edge banding. Like the melamine variety, wood edge banding is preglued with hot-melt adhesive, making it easy to iron in place. Its 1/100-inch thickness makes it flexible, yet it won't crack because it's tenderized. You can buy the presanded, 3/4-inch-wide material in a variety of hardwoods, including cherry, mahogany, maple, oak, and walnut.