There is a distinction between clone and kit. I did one extract kit, haven't really done any clones yet. To be honest, there are only a handful of commercial brews I'd be interested in cloning. If I thought I could duplicate Firestone Walker Union Jack, maybe I'd give it a shot, but I don't think the quality of their beer is strictly based on ingredients - they barrel age, and I can't.
I like to look at a lot of recipes for beers of the type I want to brew, then devise my own recipe, knowing that it is at least reasonably close to recipes that have actually produced beer. I don't see any way around an experimental period, because there is one thing that will be lacking in ANY beer that somebody else invented - tailoring to YOUR taste. I've also read most of those books that are being mentioned. Good luck.