How did you find the manga before the anime? Even now, it's so underground! Well, I didn't read the manga first like you, but I thought Megumi was somewhat sympathetic in the anime (after reading the novel though, you can bet I won't be thinking that next time I watch it). I think that all things considering, the mangaka did a good job converting a whole book into a manga, especially such an inner monologue-reliant story. The first time I watched Shiki, I didn't really notice Toshio, either; tbh, I rolled my eyes at his parts because I thought he was so boring! It was totally different the next time, though; I was absolutely looking forward to his parts. I think that's because I wasn't really interested in the story the first time; I was expecting a classic horror, but it turned out to be quite different than that, so by the time that I realized that (it took a while because I'm slow), the beginning half was over, and Toshio's medical monologues were over for the most part.
Do you read a lot of Japanese to keep up your knowledge of the language? If I knew Japanese well (or at least well enough to read), I'd get the hardest books I could and comb through them slowly with a dictionary. Or at least, that's how I imagine myself doing it. I'm all about 'Go all the way, or don't go at all'.

Aww, It won't let me see all of the art because I'm not registered, but it's really good! I'd probably understand it better if I'd finally get to watching FMA~ I feel like my Seishin drawing should just sit down compared to that, though! Also, I was expecting like, hardcore hentai but it's not even that bad, from what I saw (maybe that's because I couldn't see it all, though). It would be cool to see you draw Seishin, too!