That long-tail you mention is fairly modern. The average size of a physical bookstore has increased dramatically in the past two decades -- I wish I could find

That long-tail you mention is fairly modern. The average size of a physical bookstore has increased dramatically in the past two decades -- I wish I could find a good cite for that, but I recall the bookstores of my youth as being 1/4 the size or less of the typical Barnes & Noble today. Anything that didn't fit into that space had to be ordered from the publisher (though the bookstores were happy to facilitate that process). Amazon just accelerated the trend; the super-sized bookstores were clearly taking over the market before the Internet hit the mainstream.