I could go betting that it is possible to destroy a chair with 4 damage shatter, as I would count it as small, and fragile
Leather bound books are definately gone in a shatter, imo.
Objects do not have separate hardness, but an ac value, depending of the material, cloth and paper are ac 11, wood and bone objects are 15, and adamantine is a whopping 23.
AC is of course ignored by shatter spell
DM may also determine that if some type of damage is good/bad against something, ie bludgeoning doesn't work much on rope.
do note that shatter spell doesn't affect magical or equipped objects, ie it doesn't destroy anything on person.
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