I’ll repeat what I said down in the comments. There is no generally agreed definition of what constitutes art. We could argue endlessly because each one interprets it in his own way.
For me personally art, is something you spend time and hard physical and emotional work to produce. To achieve a great state of art you should master a relevant skill. Reading meets all of this criteria and that’s why I consider it as an art.
Thank you. What you said very much resonates with exactly how I feel about books. Your comment made me think about a crude analogy to add; let’s assume we have a big barrel filled with water. If you take a stick and start stir the surface area, only the portion of water on top will move. As you gradually lower the stick more water stirs with it. As you reach the bottom the whole barrel will move with a stick. Same with books; the more elements of mental life getting involved in work during reading, the stronger a connection between a text and what we have in our mind and feelings, and the deeper a reading.
I use Kindle, and it has a great feature of highlighting text you want. Every time I see a worthy passage I highlight it. Usually it comes to 1-5 passages per book.
You absolutely DO produce something. Just not in a regular physical sense. If reading books had no output you wouldn’t read any. The ‘production’ of the books is the gain we receive from reading them, be that a historical knowledge or an emotional happiness.