If you liked "Atlas Shrugged", you will love "East of Eden" by George Steinbeck. It has some passages on self-determination that puts anything found in Rand to shame. It's a tome, and it starts slow - do yourself a favor and make it through the introduction of one of the villains, Kathy (chapter 8 or so). It doesn't slow down after that. "The Watchmen" by Alan Moore. It may be a graphic novel, but the issues it raise…
I'll add:
"Sandman" by Neil Gaiman. Also a graphic novel, but this series literally reinvented comics to me, and to many other readers.
"Lunar Park" by Bret Easton Ellis. Probably the safest introduction to Ellis if you aren't looking for a rampant gore-fest. Spooky, creepy, chilling, but also insightful, confounding and enlightening.
"Catcher in the Rye" by JD Salinger. Mostly recommending as it fits into the above list, but I feel like it was missing. I personally felt it was overhyped, but I'm the odd man out, as everybody I've ever talked to considers it profound.