Author here. It mostly came from a personal need rather than trying to answer "what would this look like on object storage?"

I wanted something with as little infrastructure as possible, ideally no database or additional services to maintain, while still having my library available anywhere. Object storage fit that pretty well, especially with things like R2 where the free tier is already more than enough for a personal ebook library.

That said, I don’t want Bookshelf to be tied to one particular setup forever. The plan is to keep the core idea of minimal infrastructure, while adding more storage/deployment options over time.