The book that most changed my reading life is not a novel. It's C.S. Lewis's An Experiment in Criticism, which argues that the proper question to ask about books is not 'is this a good book?' but 'what kind of reading does this book produce?' Lewis's point is that some readers use books as a kind of experience and some use them as instruments for something else, and the distinction matters more than the quality of the book.

This sounds like a minor distinction but it changed everything about how I think about what I'm doing when I read. Am I attending to this book or am I processing it? Am I present in the text or am I extracting from it?

I ask this question about my own reading now, not about the books. It's a more useful question.