An expandable storage device is provided including a first panel and a second panel, along with one or more mechanisms for adjusting the size of a spine therebetween. By one approach, the storage device includes a first panel having a first panel spine portion, a second panel having a second panel spine portion, and one or more actuators, where the first panel spine portion and the second panel spine portion are configured to form a spine of the device having an adjustable width. The one or more actuators may be configured to move between an unlocked and a locked configuration to move the first panel or the second panel relative to one another and selectively retain the spine of the device at variety of adjustable widths. So configured, the device may accommodate an increasing or decreasing number of articles, sheets, or other items placed therein.