Your child reads graphic novels and nothing else, and they've asked for more. Not more grown-up, just more. Every book here is book one of a long series, every one still has pictures all over the page, and every one is short enough to finish in a sitting or two. Pick the one that matches what your child already loves and hand it over.
Let's get the awkward part out of the way, because you may have heard it from a teacher or a relative: this shelf is not about graduating from comics. Reading a graphic novel is reading. It always was. The only reason this shelf exists is that some children hit a point where they've read everything in the format and want more story than the shelf at the library can hand them, and prose is where the rest of it is. So the question was never 'how do we move them up.' It was 'what gives them the same pleasures.' That's what every book here was picked for. All of them are illustrated, and not politely, there's a drawing on nearly every page carrying real story. All of them run on short chapters and big type. All of them are book one of a series that goes on for ten, twenty, thirty more. Pick by what your child already reaches for. If they love games, Press Start. If they love diaries and doodles, Owl Diaries. If they love dragons, Dragon Masters or Wrenly. If they love a big loud cartoon fight, Ricky Ricotta. If they love a hero who is gloriously too much, Dory. One click is the whole path.