To hook readers from the start of a graphic novel, you can introduce a conflict early on. It could be a conflict between two characters, like a hero and a villain who have a long - standing feud. The art should complement this by showing the tension between them. Also, using cliffhangers within the first few pages, such as a character about to open a door that might lead to something dangerous, can keep readers turning the pages.
One way is through a startling event. For instance, a sudden explosion or a character waking up in a strange place with no memory. This makes readers wonder what led to that moment.
An interesting premise can hook readers right away. Say the graphic novel is about a world where people can swap bodies at will. Just presenting this unique idea at the start can make people want to know more about how such a world functions and what the characters will do in it. The first few panels should also be visually dynamic to catch the eye.