Short answer: it is still perfectly legal to import books into Argentina, so long as all relevant regulations are complied with.
Longer answer: The government has been doing its best to try to make it effectively impossible to import books.
The government, last week, passed a regulation mandating that any book imported must be inspected to ensure that the ink has a perfectly safe amount of lead in it. Since this is an unheard of inspection in any country -- including all those whose populations read vociferously and have never had any lead-from-ink problems -- this effectively killed the book importation market.
After intense protests from doctors, lawyers, students, and fans of Harry Potter, the government rescinded the measure. As of now, therefore, books can -- once again -- be imported legally into Argentina.
To understand the government's motives, it is important to remember that the government's objective is currently to promote Argentine industry. The government hopes that, if no books from abroad are imported, that Argentine publishers will begin publishing more books locally to compensate for the lost imports.
It is also import to remember that books are exempt from import taxes in Argentina.