Books

The problem is never on the tech end, assuming you wanted to make a good platform. That's probably a 400-level CS class project, especially if you're only dealing with a single library system that doesn't have multi-million-user-scale and five-nines reliability needs.

The pitfalls are 99% about the business relationships and having to pre-enshittify the system to service them-- getting the publishers to trust the platform will enforce DRM and related random shitty deals (i. e. that ebooks have to be retired after n loans, as though they wear out like a paperback). I'd expect there's virtually no trust for a new player.

What's needed is mandatory licensing. The libraries and their software dev partners decide what terms they want, they get a standard price card, and the publishers have to eat it.