Over the years non-philosophers done a pretty effective job of disparaging the philosophical writings of Nicolo Machiavelli's writings. Leadership scholars simply dismiss his works under the rubric of "bad leadership." Among psychologists the term "Machiavellian intelligence" refers to the human (and Chimpanzee) propensity for deception. In fact, the adjective itself, "Machiavellian," has become synonymous with deception and immorality. Philosophers, political scientists, and scholars that have actually read (and understand) his seminal works: The Prince, Discourses on Livy, and The Art of War have a much more nuanced assessment.
As you read The Prince it's important to understand Machiavelli's philosophical moorings. First and foremost, Machiavelli is a descriptive empiricist. Therefore, in contrast to the a priori, deductive, rational epistemology employed by Plato in The Republic, Machiavelli believes that human knowledge can only be ascertained via inductive observation of the world, or as Plato would say "in the cave." In other words, if you want to know how to organize a group of human beings, Machiavelli suggests that the best way to begin that process is to uncover the descriptive facts: How are sucessful organizations organized?
Second, Machiavelli is a prescriptive utilitarian; that is, he (like Plato) believes that a good organization produces more happiness than unhappiness. Like Plato, Machiavelli believed that political leadership is especially important and that "bad leaders" destroy themselves and their organizations and "good leaders" preserve themselves and their organization. Based on historical evidence, Machiavelli described how thoroughout the course of human history, leaders and followers tend to behave within certain kinds of organizational contexts. At the beginning of The Prince he identifies two different organizational contexts: republics (shared governance) and principalities (monarchy). The Prince explores the "nature" of principalities. So as you read The Prince keep in mind that he is not "prescribing" monarchy as the best way to organizise human beings, he's only "describing" the kind of behavior that you'll observe in principalities. Of course, some principalities survive for a long time, while others have suffer extinction.
Now it's important to emphasize that both Plato and Machiavelli are both utilitarians of sorts, and therefore agree that the primary value of collective life is that it brings about more happiness than unhappiness. Philosophers call this flourishment. Therefore, Plato and Machiavelli that are trying identify the underlying political arrangements that increase happiness and decrease unhappiness. Recall that in The Republic Plato attempted to prove that tyrants are unhappy and the organizations that they head are also unhappy. Well, what Machiavelli is going to argue in The Prince is exactly what Thrasymachus would have argued in The Republic if he had chosen to remain engaged in the dialectic with Socrates. In other words, Machiavelli is going to do philosophy within "the cave," in a world where humans actually possess the equivalent of "Gyges Ring."
One of Machiavelli's of The Prince is the idea that sometimes leaders have to make decisions where none of anticipated outcomes are ideal. In short sometimes leaders must get their hands dirty; that is "choose between lesser evils." Philosophers call this the "ethics of dirty hands." Political leadership often takes place within this context, however you might argue that other leadership contexts also entail getting your hands dirty. Machiavelli argued that virtue-based ethics in the Greek and Judeo-Christian traditions cannot provide moral guidance in these contexts and that "virtuous leaders" (in the Platonic sense) are deposed by followers and/or conquered by other nations. The question for you is as follows: "Are there times when leaders MUST "enter into evil" in order to avoid catastrophic consequences? If so, does this apply to other leadership contexts?"