Hi!
I found you can do it one-by-one in Wikidata Query [3] and in Wikidata Query Serivce [4] but neither seems amenable to doing a query on the fly "Get me the Wikidata item for each of these 100 ISBNs "2-7071-1620-3", ...
At least in sparql, this would be easy to do:
PREFIX wdt: http://www.wikidata.org/prop/direct/ SELECT ?book ?isbn WHERE { VALUES ?isbn { "2-7071-1620-3" "2-7071-1620-4" "2-7071-1620-5" ... } ?book wdt:P957 ?isbn }
Unless I misunderstand what you mean here.