Addiction is when something takes over your life to a degree that has the potential to damage your social relations and your job. If books do that, it will definitely be seen as bad.

The difference between books and drugs is that liking books in a non-problematic way is generally seen as good while many people will call anyone who takes certain drugs an "addict" and see them in a negative light, even though they may take these drugs responsibly and without damaging other aspects of their life.