Atlas Shrugged & The Fountainhead are terrible, terrible books. But bad as they are, it's the philosophy & the fanbase that makes them really astoundingly bad. It's not so much a proto-Neoconservatism as much as it's an idealised Libertarianism - an idea that elevates selfishness, self-interest & a class-based mentality as THE highest values to be enshrined in any society.
Couple this with the fact that a lot of people seem to read it when they're young (ie, <20 years old) - a time when the pitfalls of such a mindset are not readily visible and the (alleged) benefits are very tempting, it creates the basis for some truly misguided thinking later on in life.
It's only when they realize (and some never do) that Rands' base assumptions are unlikely, if not outright false that they start re-thinking the whole thing.