I , too, love Flatland. It's also a pretty on-point satire of Victorian society. Never got into HPMOR though. Yudkowski's writing style is kind of headache inducing, and complicates otherwise simple concepts in an effort to impress and overawe. Sometimes when the point is explained plainly, contradictions in his ideas become obvious. Like the chapter where he goes on about how "the map is not the territory", yet does the transfiguration be reifying the "map" that is quantum field theory anyways.
I agree, I'm mostly talking about the earlier chapters though. Such as before Harry reaches Hogwarts. With the basic lessons such as try to prove yourself wrong, and also figure out what evidence or arguements will change your mind. I was also enamored with the way he tied the learning experience in with the story, especially in earlier chapters. I haven't been able to find any other works that did this formulation of story and learning well. Most books, I felt like I was being talked down to. However, that's not to say that the story is a good one, that HPMOR is the best rationalist fiction, nor that one should blindly accept Yudkowski's ideas. In fact, some people claim that lesswrong, the forum headed by Yudkowski, is ironically close minded. Regardless, I found the scenes where Harry was discussing how to think with Draco or Hermione, the people who were new to rationality, great brain food. P.s. Can anyone recommend a learning story, such as described above?