People who are described as "book addicts" are almost never actually addicted to reading. It is usually meant exaggeratively to describe someone who really enjoys reading. The term "addict" gets used euphemistically to describe lots of behaviors which do not really amount to true addiction.

If someone were truly addicted to reading, I think the people in their life probably would be very concerned for them and it would be very disruptive and damaging to their overall well-being and relationships.