Serenity: Those Left Behind is a comic book continuation of the ill-fated series, Firefly, which bridges the gap between it and the feature film Serenity. The comic was originally released as a three part mini-series this past summer just prior to the film, and its main purpose is to provide proper continuity from TV to film. This past week, Dark Horse Comics collected all three issues and released them in a small graphic novel.
While I must say the art and certainly the style of writing is consistent with the Serenity franchise, I found myself rather disappointed with the quality of the storyline, as it wasn't up to the usual level of depth I've come to expect from this particular band of space brigands.
I suppose my real dissapointment is that there is no big continuity bridge with this grahic novel; it's simply another episode of the show in comic form. Basically, Mal and crew have a job that goes wrong and do what they can to find another one so they can essentially eat and keep the ship fueled; nothing out of the ordinary. The only thing clarified is why Shephard Book decided to leave the ship, however it never mentions anything about Haven, where he winds up for the film.
I also found a few other things unclear about the graphic novel's story, however I don't want to discuss them as that would give away some spoilers.
Overall, Serenity: Those Left Behind is a good comic and a good read, however it's not up to par with the quality of the show and film. It also happens to be very short, so if you're not sure if you should buy it or not, you can most likely read it pretty quickly in the store.