Both are somewhat hard books due to the sheer magnitude of hard language (The Brothers Karamazov) and dense content that is encapsulated per page (Maps of Meaning).
I think the reason why you should read hard and complex books is the same reason why filmmakers shouldn't just watch popular comedy movies. Get the taste of all movies to help you combine them to form your own.
And the reason why you should read different hard books is that you want to have human experiences as much as possible.
What is the difference between a relaxing activity and the form of leisure that constitutes the end of one’s life? The difference is simply that we would not judge a cookout or the beach holiday or card playing to be the pinnacle of life. These activities are lovely, human, and necessary, but they do not draw on our highest capacities. Art, music, serious conversation, and loving service, by contrast, bring out the best in us. They are goals toward which we strive; they are engines for limitless personal growth. The difference between leisure and recreation will be subtle, but clear, in how we choose these different kinds of ends. Any minimally happy life must include recreation, but what really matters is far more demanding. - Lost in Thought by Zena Hitz
I really feel like you should not be surprised by what you experience in life, and you do that by reading about it.
Those who have seen the darkest moment can truly appreciate the light.
Read about those uncomfortable moments in-depth to read about the struggles of those that make your suffering merely an obstacle.
Studying history makes us appreciate the importance of today's freedom that we take granted for. Forgetting about struggles would be a great insult to those who have done the ultimate sacrifice for you.