The best time to read Atlas Shrugged is pretty much never. You're not going to get more out of the game by having read Atlas Shrugged or any of Ayn Rand's other books first. Yeah, it is a dystopian using a failed objectivist society as the backdrop, which is completely awesome, but as long as you have some grasp on the concepts of objectivism you're not going to miss out on that angle of the story.
Not to dis on Atlas Shrugged, it is just kind of a long tedious read, and it really isn't that great.