As troisoiseaux said, the Horatio/Ophelia romance for sure was a surprise; also the take on Hamlet-the-character (a shockingly un-self-aware variant and one I was surprised by and found myself mildly indignant about; it's not that I love Hamlet the character particularly but I do think he's got more going for him than that!); also Strength and Patience of the Hill definitely anti-ships both Hamlet/Horatio and Hamlet/Ophelia in a way that feels a bit hilariously like weapons drawn on the entire Hamlet fandom. (A while back when I read it I ended up concluding that one of the interesting things to me about the book as Hamlet fanfic is the way that S&P, despite being generally so careful about language, is willing to make very definite claims about things that are very deliberately ambiguous in the play.)