Just needed a little more detail. 
 This is the first little novella in the 'I Hunt Killers' series and while it's a perfectly fine read, it feels like somewhat of a missed opportunity. You see this novella acts as a sort of prequel to the main trilogy, and shows you how the local sheriff G. William (a good character from the series) went on to catch the towns first ever serial killer, Billy Dent a.k.a Jasper's dad. 
 This is an extremely short novella coming in at just under 80 pages, and a lot of that is sort of background information on the sheriff, as opposed to details of the investigation into Billy's original reign of terror. We learn that the sheriff had recently lost his wife, and that it was an election year during the time Billy was caught, but ultimately it isn't as interesting as the full investigation could have been. 
 When the sheriff finally does start to connect the dots, the whole thing seemed a little rushed, and figured out a little too easy. It was like all of a sudden the sheriff stands up and shouts 'IT'S BILLY!', simply because Billy said something rather vague that could have implicated him, yet also, could mean absolutely nothing. 
 Overall, this novella isn't really needed to enjoy the original trilogy and I don't think it really adds enough to the plot for it to be an 'essential' read. I'd say pick it up if you really love the series (like I do), but otherwise, you aren't exactly missing much. 2/3 stars? 2.5.