Act I Scene 3 - The Banquet

The Banquet has probably the best explanation for Ophelia being warned off Hamlet I've ever heard. It's all about politics, though in the play, no one would ever explain it to poor, innocent, apolitical Ophelia. But the father in The Banquet does:
When Hamlet Sr. was king, a match between Hamlet and Ophelia was a good thing for the Polonius family. Now that Claudius is king, and Hamlet has fallen out of favor with that regime, any alliance with the Prince may put the Polonius family in political jeopardy. Polonius is nothing if not a political creature. It also helps explain why Gertrude goes on about marrying Hamlet and Ophelia after the latter's suicide. On the Hamlet side of the family, this was seen as a good match. But Polonius would not have expected the same reaction from Claudius.

Speaking of Gertrude, the dialog here goes on to make a point about mirroring the play's two women:
"My heart will never change."
"Make it change. Learn from the Empress."
In this reimagining of the play, Ophelia's father asks her to change her heart, just as the State asked Gertrude to do the same (in line with the unwilling wife aspect of this version).

All interesting notions as we delve deeper into the play.