Popular in town as much as on the paths less traveled, there are no boundaries as to where you can deploy a Book Pack... It's a versatile pack design that will hold up to years of use and abuse. The standard Book Pack is a "box-style" pack where there is an extra panel between the front and back of the pack. It has a gusset. The Simple Book Pack is a traditional envelope style pack. There is no gusset. The front is sewn directly to the back of the pack. Small, trim and streamlined, you can almost forget you're wearing this pack with a small load.