If you want an easy read of substance that you can just dip in and out of, why not go for shorter fiction?
Because they’re largely in the public domain, you can pick up the complete works of Edgar Allan Poe for very little. I’m recommending him not just because he’s amazing (and he is), but also because you mentioned upthread that you like crime/thriller. With The Murders in the Rue Morgue, Poe basically invented the detective story. So if nothing else, this you can see where your favourite genre began.
But beyond that, he has adventure stories, poetic meditations on life and death (mainly death), some of the most suspenseful fiction ever written, and in The Fall of the House of Usher, my pick for the single greatest short story of all time.
Already read Poe? Never mind. Never more.