To be honest, Amazon shipping works because it's a monopoly. They don't care how much you buy, it's almost the same for the company, they have to hire the same amount of staff, and same paid hours, at least in urban area. But for any independent store, they have to negotiate a rate with a shipper, which would charge a flat base rate, and overweight if there are any. So it can be difficult for them to offer quality and fast shipping in terms of cost. In a way, they are less efficient than Amazon.
Bookshop fulfillment is handled by Ingram Content Group, a massive book distribution and logistics company, and itself the biggest distributor to independent bookstores.
