Serious socio-economic criticism cannot find its base in the writings of Ayn Rand. To do so would be akin to basing legal theory on the writings of John Grisham, or Renaissance scholarship on the work of Dan Brown. While there's no harm in reading Ayn Rand's work in itself, one must keep in mind that Rand is a writer of fiction, of imagination, not philosophy.
That others use Rand to propose capitalism as "the only just system" (Aug. 13 letters) is a reflection of her value as a fiction writer, not a philosopher. It is only in fiction, in imagination, that one can conceive capitalism as a "just" system. If we examine global class relations, we are hard-pressed to claim that the division between the haves and the have-nots is a "just" one.
Exactly why do more than a thousand people "deserve" to die in a garment factory collapse in Bangladesh, while we "deserve" to go to Wal-Mart and buy the clothing they died sewing? Because they didn't "work as hard" as we do, their lives are somehow "worth" less than ours? I suggest defenders of capitalism take a 16-hour shift chained (sometimes literally) to a sewing machine in a sweltering building and then decide if they're opposed to "shackling regulations." This is the reality of capitalism.
If you're looking to read about "just" capitalism, look to fiction: look to Rand. On the other hand, if you want to read a real work of philosophy dealing with capitalism, read Karl Marx's "Das Kapital." Marx is, after all, the person who defined the "system" of capitalism. It will be abundantly clear in the first few pages the difference between philosophy and fiction. In the realm of fiction, we might argue that capitalism is what's best for all people, but in reality -- the concern of philosophy -- we see the truth that capitalism, while a real socio-economic system, is anything but just.