sadly - i think they compliment each other, and at around 15 quid each on amazon - both a good deal
I've just made the upgrade from CS2 to CS5 and will be able to give more time to my photography so I want to learn more about the program now. I've ended up buying both books because the summary above is spot on; the Kelby one is more about getting from A to B and the Evening one delves deeper into how and why you get from A to B. I can see both being useful.