What is central to literary meaning, or the meaning of any work of art?

Sometimes when I read philosophers on this topic I wonder how their theory would work in practice, or even what they are actually thinking of.  Some philosophers seem to be telling us that we are not supposed to pay any attention to what the author says about the meaning of his/her work.  Yet I just saw an excellent commentary on a film by the director that made me appreciate the film more than I did before.  So am I being told that this is not a legitimate experience, or what? Jerrold Levinson holds to a view called hypothetical intentionalism which says "the core meaning of a literary work is given by the best hypothesis, from the position of an appropriately informed sympathetic, and discriminating reader, of authorial intent to convey such and such to an audience through the text in question" and this means valuing "optimal hypotheses about authorial intention, rather than actual authorial intention." I confess that I have no idea how to make sense out of this idea.  If you are trying to come up with the optimal hypothesis about authorial intention you are trying to come up with an optimal hypothesis about actual authorial intention.  What other intention would this be about?  It is true that your best hypothesis about authorial intent might not actually capture actual authorial intention, but you would only know this if you knew what the actual authorial intent was, but then in that case what you knew would then be your best hypothesis.  This seems to me to be remarkably like the lier's paradox.  From what Levinson further says I gather that the problem is that if actual intentionalism were true then the literary text would be no more important than the author's diaries, etc. in determining the meaning of the text.  This is a more subtle issue.  What is seems to assume is that somehow the meaning of the text is independent of contextual knowledge of the reader.  Gregory Currie, an ally of Levinson's on this point say "an interpreter for whom letters [etc.]...have suggested an interpretation of which the text is a defective embodiment has ceased to be an interpreter of the work in question..."  However Currie fails to see that if I had read the letters etc. before reading the text then I would naturally see the text in terms of that contextual information, and if the text is clear to me under those circumstances then it is hardly defective.  It is no more defective than if I read some other writing of Kant before reading the Critique of Judgment and then read the latter work with understanding others might not have!  My quotations come from Jerrold Levinson "Defending Hypotehtical Intentionalism" British Journal of Aesthetics 50:2 (April 2010) 139-150, pp. 139-140.