The main problem with a database for this project would be if you wanted to store it all on the blockchain. Book listings need to be updated as new editions come out and Steem doesn't let you update older posts. Would it be possible to only store the book listing details on your side until a review is posted then transfer the listing data to that post? (not a developer, so not totally sure). @carn

As to the database/blockchain compatibility issue, I'd make each edition a separate database entry, because in the ISBN database, they already are. But I'd connect the entries, using the (some method someone who actually understands how this would work could figure out). @didic

You're both hitting on an interesting point. Linking reviews across individual book editions to an overarching book will be tricky but should be possible.