I've written before about how just reading things you know you like is limiting, and that you should always try to expand your horizons, but that knowing what you like and what's comfortable is super important, and there's nothing wrong with sticking to what you love. So which is it? "Read outside the box" or "stick with what you love"?
Um... a bit of both, really.
See, here's the thing, and I want this to be super clear.
When I advise reading things you're not sure you'll like, reading new things or new genres, I'm not saying "Go out and find a book that makes you uncomfortable and read it." I'm saying that there are techniques used by authors outside your usual favorites that might be new to you, and help you learn more about writing and the things that you like to see in stories.
But this isn't "how to read good," this is "how to learn new techniques for writing good stories." If you're reading for pleasure, there's nothing saying that staying in a genre or sticking with known authors isn't a bad thing. You can't read wrong.
The thing to keep in mind is that while you can always dig deeper into fiction you love, there are techniques that particular story doesn't use that you might find really useful. You might even find new stories or authors or genres that you love as much as the old ones.
So when you look at your checkout history at the library or the "To Read" list on your Goodreads account and try to figure out if you need to expand your horizons, just ask your self why you're reading. If you're reading to learn, then maybe some new books from different authors or different genres might help. If you're reading to de-stress after work, maybe sticking with the ones you love will be better at helping you unwind.
There is no wrong way to read. Enjoy it. :)