I would figure out what your reading level in English is and aim there or a little higher. Schools here use lexile levels, you could test yourself and aim for that level and stretch just above it.

Or, If you want to practice reading books at a higher level, choose something that you’re really familiar with in Portuguese (or another language you’re very competent in). If your spoken English is good, and your written English is as good as it is here, I think it will only take you a short time to be reading the type of books you are interested in.

You could also pick up a literary guide to the novel and read that alongside to get a better understanding as you go along.