vcard:AddressBook is not defined in vcard-rdf.
vcard:AddressBook is used in the context for solid:forClass in the Type Indexes specification. References to "address book" should use vcard:VCard (as in the case with solid:forClass).
Noting that #26 proposes to use TI for "high level index" so that libraries with domain specific indexes can be referenced. While an address book is among a good example of such index, it can't be expressed with vCard as it stands without introducing new definitions (vcard:AddressBook or another).