> I just can't quite figure out what Bookshop offers that your local bookshop does not offer

In short, Bookshop is a tool that good local shops can use to boost their chances of making a sale.

Bookshop is a great resource for indie stores that focus on promoting local authors and therefore have less in-store space for James Pattersons or Colleen Hoovers. If a fan of those books passes through town, however, the bookstore can still make the sale and gain a customer through bookshop.

It's great for niche bookstores. I visited a small bookstore in Utah once that focused on mining history, Terry Tempest Williams desert ecology stuff, and touristy coffee table books of Utah scenery. If Bookshop had been a thing then, I could have asked for a copy of A Man Called ove, and they could have said "Sorry, we don't carry that one, since it's not Utah related, but you can order a copy here," and hand me a card for bookshop.

It's also a lifesaver for used bookstores. They tend to have little control over the books they have. Of course, they decide what to keep and what to put on the shelves, but they can't just magically make Brandon Sanderson books show up. At best, they can have some kind of request system that will flag books and send a notice to a customer. Being able to still sell a book without setting up the entire enterprise of a new bookstore is a saving grace.