Slow down and ask yourself questions as you read. Consider the narrative technique the author is using. From what point of view is the story being told? Do not skip over the prologue or epilogue. A novel reveals itself slowly. The choice of words and how the story is structured was carefully planned. Little is left to chance.
Look up unfamiliar vocabulary for the meaning and context. Do not skip over a dialogue or guess at definitions. Keep a pocket dictionary handy. Some electronic reading devices have built in word finders. Use the feature whenever you can. Alternately highlight a passage for future reference or mark the page.
Join a book club. Getting feedback from other book lovers opens you up to other perspectives. People can read the same chapters and have different interpretations and pick up details you might have skipped over. Jot down notes. Sharing your opinions on a regular basis will make you read more critically.
Research the author and his background. How does it color his writing style? People base stories on their own life experiences and cultural upbringing. Read the jacket flaps and author biographies available. Follow an author's body of work and you will anticipate their next novel more. Attend book signings and in-person readings by the author.