Writing a good book does not equal writing a good comic. Or a movie. Just like making a good music video doesn't mean you can direct a movie well.
Talent just doesn't always carry over. King's a decent writer...great by some estimations. I kinda sorta enjoyed the first two or three Dark Tower books. After that, I lost interest, got bored. I never really cared for anything going on. I never felt like "oh, NO, what's going to happen NEXT?" More often, I was feeling "when will this book end?"
I don't know that King's proven that he can translate his talent to comics. PAD, on the other hand, has demonstrated that he CAN translate his talent to books. So the question is, can he apply that to translate a book into a comic? I'm guessing yes.
Still, I'm not getting this. I'm slightly interested in supporting book-comic conversions, just so we can see more of them. But I don't think my budget can support all of them. I'd have to get near the entire Dabel Bros. line, and aside from the Anita Blake series, I'm just not interested in the other properties.