Overall, a good continuation of Firefly. Those Left Behind takes place between the Firefly TV show and the Serenity movie. As for the artwork, the characters don't look quite like the actors in some of the scenes. But there are also full page shots of each that are very close to their likenesses.
They're also able to be a little more violent in here than they were in the show. The action resolved super fast, but I guess if you consider this as one episode it makes sense. As a Firefly fan, I definitely would recommend this graphic novel, even though it's short and leaves you wanting more.