Patent ID: 7661715

Claim:
A book comprising: a stack of sheets, the stack having a thickness, a binding edge and an opposed non-binding edge; a binding region defining a cross section through the thickness of the stack and substantially parallel to and proximate the binding edge, the binding region having a first stack density; a second region passing through the thickness of the stack between the binding region and the binding edge, the second region having a second stack density, the second stack density being greater than the first stack density; and a resilient binder in compression around the binding region; wherein a portion of a first sheet in the stack is perforated in the binding region of the first sheet and a portion of a second sheet adjacent to the first sheet in the stack is perforated in the binding region of the second sheet, at least some perforations in the second sheet are misaligned with perforations in the first sheet and the perforations in the first sheet are intertwined with non-perforated sections of the second sheet to interlock the first and second sheets together.