The law (BuchPrG) provides a rationale to restrict the free market in this particular case in it's first section (translation by me):
> This law provides protection for books as a cultural heritage. Fixing prices for customers ensures availability of a wide range of books. Additionally, this law ensures that this offer is available to the broad public by encouraging the existence of a large number of stores.
Fixing the prices makes books more expensive but ensures that even small niches are filled that would otherwise be unprofitable and bookstores sell those. It's supposed to be a cross-subsidy by buyers of popular books. Additionally, almost every book store will sell you almost any book (if it isn't in stock they get them overnight).
I think around half of the EU members have such laws in place. It is widely debated whether the law has the predicted effects.
> This law provides protection for books as a cultural heritage. Fixing prices for customers ensures availability of a wide range of books. Additionally, this law ensures that this offer is available to the broad public by encouraging the existence of a large number of stores.
Fixing the prices makes books more expensive but ensures that even small niches are filled that would otherwise be unprofitable and bookstores sell those. It's supposed to be a cross-subsidy by buyers of popular books. Additionally, almost every book store will sell you almost any book (if it isn't in stock they get them overnight).
I think around half of the EU members have such laws in place. It is widely debated whether the law has the predicted effects.