To my mind, most errors in interpretation involve looking at a part of a text not in relationship to the relevant whole.
In this regard, Nick White's Companion to Plato's Republic, which I've been using this semester, contains these sensible remarks in the Preface, which I might easily have missed:
I believe that the overall argument of the Republic can best be seen, and mistakes about its components best avoided, when the argument is seen as a whole. Moreover, I believe that this is the way in which one may gain from the work what is philosophically most interesting. Many recent scholarly discussions of the Republic suffer from too much concentration on what are thought to be its crucial sections. The fact is that the details of Plato's arguments are often (not always) much less interesting than the overall scheme within which they are placed. Far more important is the basic structure of his position, which can frequently be defended through means somewhat different from the ones that he himself adopts...Furthermore, the whole point of the more detailed pieces of argumentation is easily missed if their places in the whole are not scrupulously attended to. (2)Then White adds, most admirably:
I had better explain, lest someone form the wrong idea, why the overall coherence and meticulousness of Plato's argument strikes me as so interesting. Part of the reason is the spectacle of it, pure and simple. The argumentative structure of the Republic, quite apart from its soundness or lack of it, is simply a beautiful thing to behold, the more so because it has often been so difficult to uncover. (One learns not to be surprised when a formerly aimless-seeming Platonic passage turns out to be making a point essential to the argument.) (3)(He then goes on to explain--if you want to know--that the other reason is that White has a basic sympathy with Plato's notion of goodness, that "he was right to try to disover a single notion of goodness underlying the apparent multiplicity of our uses of the word 'good'"(3).)