The Apology is Plato's version of Socrates speech given at his trial. At the time it was written, it would not have been expected to be an exact account of what Socrates said. It is, therefore, hard to know how accurate it is, but this does not really matter.
The speech is interesting for its political and historical context, but it is most important as the first great rallying cry for philosophy, truth and reason against the forces of oppression and ignorance. The triumph of rationalism and humanism broadly construed dates directly back to this speech. In the west most great thinkers who became, or almost became martyrs for free thought would have been aware of it and the long history of free thought stands on the speech as a rock.
The speech is a defense of the examined life. It famously states that the unexamined life is not worth living. It is a great work of literature. It has retained its relevance for two and a half thousand years, and it is just as relevant today. There is a certain tendency to see this battle as having been won. Or at least that the only threats are external. I think that there will always be forces that are opposed to the kind of intellectual stance that Socrates advocates and that even within modern western states that this battle is continually raging. The struggle for an ethical meaningful life is eternal and the forces opposed to that remain strong. As Socrates makes clear this battle is fought not just within the state an wiothin society, but within oneself.
One could see the speech as naieve, but I think that it is anything but. The people that I admire most in history, from Spinoza to Orwell, from Galileo to Nabakov fought this fight and it is ultimately the only fight worth having. It is eternal and the Apology will always be the rallying cry. For whatever it is worth, currently, I see this fight as being lost and that things are moving backwards because in a sense rationalistic scientific liberal humanism has lost its way.
The Apology is first and foremost a manifesto and it is as far as I am concerned, the first and best manifesto always destined to be revolutionary in its import. Probably the most important book of all time.