Indispensable.

If a book truly interests me, I cannot follow it for more than a few lines before my mind, having seized on a thought that the text suggests to it, or a feeling, or a question, or an image, goes off on a tangent and springs from thought to thought, from image to image, in an itinerary of reasonings and fantasies that I feel the need to pursue to the end, moving away from the book until I have lost sight of it. The stimulus of reading is indispensable to me, and of meaty reading, even if, of every book, I manage to read no more than a few pages. But those few pages already enclose for me whole universes, which I can never exhaust.
- Italo Calvino