Different kinds of reading require different levels and kinds of attention and commitment, and there are doubtless varying opinions on the subject. Here are some guidelines I find helpful:
1) As a general rule for all types of reading, I want to read attentively, by which I mean I want to be as undistracted and engaged as possible, with an open mind, yet alert to discern and interpret what I’m reading in the light of such truth as I am able to grasp.
2) When reading academic works, essays, or any kind of book far enough removed from my own time and experience to contain a significant amount of vocabulary, allusion, or ideology unfamiliar to me, I like to have an appropriate reference book on hand – a dictionary, Bullfinch’s Mythology, a commentary, etc.
3) Fantasy particularly, and all fiction to some degree, I think, demands what Samuel Taylor Coleridge called “willing suspension of disbelief, which constitutes poetic faith,” that is, a conscious setting aside of the laws of our universe and an intentional acceptance of the reality contained within the story which make it possible for the reader to fully enter into the fantasy realm despite its implausibility in our everyday world.
4) It is, strangely, hardest for me to describe my approach to reading poetry, probably because I read it every day, in every mood, and my experience of a poem depends largely upon my frame of mind and condition of spirit when I read it. At the heart of it, for me, is a sense of belonging, of sharing the intimate feelings of close friends I will never meet in this world.