The purpose of a short overview of only twelve serial killers escapes me, because I presume there are tomes referencing every single American serial killer (or at least most of them) and acting as introductions. I was testing Kindle in my phone the other day, and this was available for free in Amazon's Kindle books, so I figured I wouldn't be losing anything by at least trying this out.
Well, I did finish this, since I was morbidly curious about how much the level of craziness would grow, but otherwise I have to say I wasn't particularly impressed.
Obviously, there are interesting details here. John Gacy performed as a clown, and was known as an outgoing and succesful businessman. One of Jeffrey Dahmer's drugged victims escaped and the police believed he was his lover, because Dahmer (who worked at a chocolate factory at one point) was so well-spoken and calm, but if they had checked his apartment when they escorted them back there, they would've found the decomposing body of one of his latest victims on the bedroom floor. Well, later this happened: "There's a goddamn head in the refrigerator!". Ted Bundy worked at Seattle's Suicide Hotline crisis center, and earned a commendation from the police for saving a toddler. David Berkowitz had no success with women, so he decided to off them instead.
All these, however, I'd rather read from a proper and coherent reference book, or from an individual biography of one of the killers. Keller's approach is much too simplistic and, as he admits, subjective. A bit more polishing would have been great, too, since there's repetition in the parts where the victims are listed. It's all and well to note every single victim and treat them with respect, but at least a bit of variation sentence-wise would have been nice. I found no reason why one should read this instead of a Wikipedia article.