I watched the show before I read the books and liked it. Now that I've read the books, the show is disappointing (and canceled).
The show did lead me to the books. I read the first chapter on Jim's site and didn't like it. Years later I read it again, and thought it wasn't bad. Then I read the rest of the book and series. I still consider the first 3 books to be the worst in the series. I'm not sure if I like
Summer Knight or
Ghost Story more, but I think if one was to plot the quality of the books on a line graph, it would look a lot like a line graph of the number of chapters in the books on a line graph. (An upward trend).
Or if they managed to produce something good, cancel it right away.
I consider that to be a sub set of "messing it up."
I'm not very familiar with the source material because I really don't like comic books as a medium, but until
Game of Thrones, the only decent TV adaptations that I had seen were Fox's
Spider-Man and
X-men.
Game of Thrones was the first decent TV adaptation I've seen that was not for children. TV adaptations have been like movie adaptations; some of them are good if you aren't familiar with the source material.
Anime might be an exception, but I'm not familiar with the source material, and it's arguable whether or not it's for children. The arguable parts being "for" and "children."