Only ever tackled Rand's Atlas Shrugged. I did enjoy it, but find that I have to be in a certain frame of mind to re-read it......same with the Thomas Covenant: Unbeliever series.
But then again, I am a little bit of a moody reader. I can't just pick up any old book, at any old time and read it. I have to be "in the mood" for that particular genre/author.
And I never did do well with the "you must read this" situation. The "it's a classic" just makes me that much more resistant to ever picking it. Mulish Monk, that's me.