Those Left Behind is a graphic novel from Dark Horse set between Firefly and Serenity. Captain Malcolm Reynolds and his crew are just trying to get by, do a job, and find some quiet when an enemy from their past comes back to seek revenge. 
 I really enjoyed this and was sad by how short it was. The story is just what one loves to see the gang snarled in and gives fans an idea of what occured between the show and the movie. The artwork was lovely even though I had heard mixed reviews about it. My guess is because the graphics are based off of the characters/actors from the series itself, rather than completely imagined. In some places it felt a touch too dark or shadowy but not really in a negative way. The crew had it's perfect level of banter, danger, and kinship. 
 Also, the introduction from Nathan Fillion was quite adorable and touching.