I'll have it be noted that I did not bring up the genetics. I just rolled with it once it was brought up.

Nor do I actually re-read Martin's works, although I do look things up and read Wert's re-caps and re-read the family appendixes to refresh my memory of who folk are. I have read each book only once over 15 years, and I'm watching the show, now, with my husband and now daughter, the show causing my husband after the first season to read all the books and my daughter now more slowly working her way through the first book and immersing herself in that geek audience online devoted to it, which is not really 5% of the audience but probably about 50% of the audience. It's the size of fantasy's core fan audience that allows there to be a category fantasy market and for that market to be quite huge. Martin is king of fantasy land at the moment, whether he likes it or not.
Martin does, however, like SFF fan readers. He wrote the series for them. He wrote something he thought would never be produced on film. He wrote a giant epic that got bigger as he went, but he's always known the ending, as most fantasy writers do. While it was expected, back in the late 1990's, that the books would do well, given Martin's standing in the field, and might appeal to non-regular fans, it's gone well beyond what anyone was expecting. And the extent that the series and now the show are talked about on the Internet is enormous. But would Martin torture his main fan base? Yes, especially as he started it out in 1996. Most of the fantasy authors would and do.
I have talked about little details concerning the series and about Martin more than I normally would have because Martin fans are obsessed. And the show has just created an entire new, bigger group of obsessed people. Does Martin have to produce hundreds of symbols in his books for the average reader? No. Does he do it anyway? Yes. Put it this way, I trust that most that is in Martin's work means something, but I don't trust him about what it means. He's one of the few writers I've read who can sneak things in on me, despite dropping lots of imagery clues. So I don't trust the possible truth of Jon's parentage based on clues for alert readers. I do, though, agree that who Jon's parents are has an impact on the plot.
Bookmarks