The problem with learning photography in general is that it's intimidating. Most books will describe esoteric theory, and that drives most people nuts. If I'm any representation of a normal photographer, I'll look at a photo and go "that's awesome - how did they do that?" and want a nice example without having to dive into theory and other things. I just want to take the best pics possible that I can with what I have.
The layout of the book is rather simple - like a cookbook. There's a great photo, and then a description of how that photo was taken. The strength of each example is that it's not only easy to follow, but it explains enough theory for you to understand concepts and apply that in other situations. Most books don't do that - they'll tend to lose you on specifics.
Kelby's books are written with the beginner in mind and would even reach into those with intermediate skills. I don't think that seasoned professionals would learn much from these books, but they're worth their weight in gold. The Digital Photography book series is what I recommend to those who are interested in doing more with their cameras and photos. Not all of us can be professional photographers, but we can make our images look better than they are now.