I love the Percy Jackson books. I love the story, I love the characters, their development and the worldbuilding - you can read my full review of the first book right here - and all the other books by Rick Riordan here.
Why am I telling you this? To make you understand just how disappointed I was when I read the graphic novel and found that it was a weak watered down version of a great book. All the small details that make the big difference in the long run have been left out and we're left with the gist of the story - but without the explanations, the feelings or the general understanding of who, why or what the hell. And that's just a damn shame. I hope no one reads this rather than the actual books.
The illustrations/the art style is nice enough, but also rather generic and everybody was depicted as very... handsome. Nobody stood out, and I doubt I'd be able to identify any characters from a line up.
So all in all - :( very disappointed, very unsatisfied.