In many ways, this echoes the earlier days of RPGs, when a photocopies set of rules was 'a viable product'. In a similar fashion, items one step up from photocopied pamphlets are still standard items. Most other books are limited run small press. They have very high prices and small quantities. They often sell directly from the author.
Magic books are, like RPGs, hard to find.
Unlike RPGs, though, this is intentional. There's a lore-like aspect to finding a good magic book. Getting to these shops is often tricky. Email lists and web sites provide a bit more leads on good books, but you still have to hunt. And word of mouth is still the best way to learn of items.