>>9720355
You're doing almost exactly what you're supposed to do.
Only point I'd give is not to get caught up in visualizing characters and scenes, as you'll find such details are usually irrelevant. Instead, dedicate that time and energy to understanding major themes, plot elements, deeper points of characterization, symbolism (if you feel it's there), devices of metonymy and metaphor, prose style, etc. You'll find that you enjoy reading books a lot better.
Also, I find that getting through a book is a lot easier when I'm reading two or three at once. If I find myself slogging through a chapter more than I should, or if one writer is starting to get on my nerves, I can always take a break without losing time. I usually can read an average of a book a week or more at that pace, rather than the month it would usually take me.
And don't read fiction exclusively. Take your time to read history, philosophy, science, theory, theology, primary sources, even quality pieces of journalism, biography, and memoir. Absorbing a diverse range of texts means that you'll have a broader set of tools with which to approach a text, whether literary or no.