Prediction: a year after HPatMoR is finished, newbies will be as reluctant to read through it as they are relucant to read through the sequences now.
I tried to get my brother to read it, and while talking with him, we realized that the story had become longer than many of the Harry Potter novels themselves. It's sheer length is going to turn people off; he said he'd have to choose between reading it or reading another Discworld novel, and I didn't have a very good answer to that.
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