I wrote a paper on this in college, and while some analyses of the Prince conclude that it was not meant as literal advice, it has little hard evidence.

Some of the evidence is in the form of supposed contradictions within the Prince, as well as from The Prince and another of Machiavelli's works "Discourses on Livy", analyzing the Roman political system and its use in the modern day.

Some of the statements made in Discourses seem to contradict suggestions in "The Prince".

For instance, in Chapter 26, Machiavelli argues that vilification and abuse create hatred, and that this makes them useless in the end. In Chapter 30, he says that a truly powerful leader will not acquire real friends through money and force, but through virtue.

However, in the Prince, Machiavelli famously encourages leaders to not govern on emotional or moral grounds, but through what will be most effective in acquiring and maintaining power. He also supports using force over kindness to secure loyalty and power, arguing that "it is far safer to be feared than loved if you cannot be both", and that "if an injury need be done to a man it should be so severe that his vengeance need not be feared".

Now, it is important to consider that the Prince was distributed in 1513, so likely written somewhat earlier, while the Livies was written in 1517.

The argument is that The Prince must have been satire or ironic because Discourses on Livy is so different. The problem, to me at least, with this argument is it assumes, without much evidence near as I can tell, that Discourses is representative of Machiavelli's true views, not the Prince. That may be true, but I have found little in the way of convincing arguments to that effect.

Now, it is possible that Machiavelli changed his views, and Discourses on Livy was his views after study and thought.

We could be missing something, and perhaps Discourses is a synthesis.

Other arguments as to the purpose of The Prince include the suggestion that the advice was designed to lead to the undoing of a ruler if the book's suggestions were followed. Things like not satisfying the people with liberal reforms, arming the people, and advising the ruler to live in his city. However, the conditions under which these things would result in revolt are mainly specific to Florence, and so the argument loses value if it is expanded to a wider readership.

Another alternate reading is that the book was not actually intended for the ruling class, but those people wishing to establish a new ruling class, in a sort of pre-communist peoples revolution. This theory, unsurprisingly, is espoused by Marxist commentators, but to me it holds little credibility. The literacy rate was not sufficient for a book to be an effective method to disseminate information among the people, not to mention the fact that The Prince has a decided air of elitism, being advice to Princes. Not exactly the people's guide to revolution.

So that's a short summary of the different interpretations and their justifications.