Objectivism holds that reality exists independent of consciousness; that individual persons are in direct contact with this reality through sensory perception; that human beings can gain objective knowledge from perception through the process of concept formation and inductive and deductive logic; that the proper moral purpose of one's life is the pursuit of one's own happiness or rational self-interest; that the only social system consistent with this morality is full respect for individual rights, embodied in pure laissez faire capitalism; and that the role of art in human life is to transform man's widest metaphysical ideas, by selective reproduction of reality, into a physical form—a work of art—that he can comprehend and to which he can respond emotionally.
Reading this, especially the bolded portion, it should be apparent than I'm not an objectivist myself. I am a fan of Rand's work, and of some of the principles of her philosophy, but mostly only as they apply to macro-scale systems like economic or political systems. On that level her philosophy is coherent and potent. Rational self-interest, it turns out, is an excellent principle to build an economic or political system around. It results in preserving the most autonomy and liberty for the individual, and results in creating wealth, prosperity and relatively high standards of living for all who engage in the system. Such a system also encourages human ingenuity, and results in life-bettering technological advancements in a variety of fields. Her philosophy as it applies to these macro-scale systems is not just theoretical, but has been tested historically. The success of laissez-faire capitalism in tandem with a representative democracy is a matter of historical record.
However, when you attempt to apply these principles on a micro-scale i.e. to personal morality, her philosophy breaks down. When you take it to it's logical conclusion, which Rand does quite literally and unapologetically, it results in declaring altruism an evil, and selfishness morally right. Though this strikes most people as self-evidently wrong, and it is wrong, the reason why it's wrong is not because the principles of her philosophy have no merit. They just don't apply to personal morality.
The way that she attempts to rationalize this position is essentially just semantics. That is, she doesn't actually think altruism is evil. She declares the subversion of one's own will for the sake of another individual's will, or a collective will, as evil. She doesn't really think self-sacrifice is evil, when you press her on it. Because if you feel it is right to sacrifice something for someone else, well then, that sacrifice is coming from your own will, and that doesn't qualify as altruism to her. So even in this I have sympathy for her position, and it does make sense to a large extent. The will of the individual should not cede to other individuals or other collective wills. Which I believe is true. Of course, as a Christian, I believe in sacrificing one's will to a greater will, but not to the will of another person, government or institution. Which is what she's essentially advocating against.
footnote: For those unfamiliar with her, her most popular, full presentations of her philosophy are found in her novels Atlas Shrugged and The Fountainhead.