Possible Clues:

• Poppable packing material
• Material popped up: three books with real worth initially condemned
• Purchase protection, but may get popped eventually!
• Article of outerwear for a champagne drinker?
• Wasted in pub bar, beaten boxer's packed it in?
• It might pop in the post office
• Shipper's supply
• Packing material (which can be popped!)
• Protective cover given criticism after blurb oddly wasted
• American boy made sound with knock to get protective cover