I thought it was bad ass, as in, really good. I thought it was another great book about SOF, along with all the other ones that many here recommend (Beckwith's, Haney's, Blaber's, etc). May I ask the folks that didn't like it, what you thought was bad about it?.
PS: I also have a book about the invasion of Grenada and the ISA is actually mentioned by name in the book, which surprised me because it was actually published in 1983.
A lot of the info in Killer Elite is pulled from other books. Namely, Secret Warriors: Inside the Covert Military Operations of the Reagan Era, Killing Pablo, and Not A good Day to Die. There's also a host of online news articles, on the ISA, including declassified unit histories; There are a couple pretty good articles in Soldier of Fortune (back when they spent more time concentrating on reporting military conflicts, and less time with the government is coming to gets my gunz); and even Discovery Channel had a program with a segment on them back in the early 90s (the program was about the us of special operations and intelligence units).
It's boring and while historical doesn't really offer an inside look the way books like Inside Delta Force did. Personally when I read books like this I like a bit of history mixed in with a day in the life of coupled with some no **** there I was stories.
The title makes it sound far more interesting than it is. From what I recall, it's primarily about the nuts and bolts, day to day political maneuverings of the unit's founder in his attempt to get the unit off the ground. The only OMFGDELTA moment was like one very brief mention of the "shooters" in the unit, and then they are never mentioned again. I was bummed that that avenue was not explored further to spice things up, but I guess they didn't get in many shootouts.