I'm in the U.S. and purchased a boxed game of DKS (PC DVD) back in January - not sure why you still haven't been able to get a copy.
I like having strategy guides for my favorite games. I mostly like to use them after my first playthrough to find things I may have missed.
But I also like them from a game collector perspective - the strategy guides provide the most complete record of information about a game you have in your library - invaluable after a decade or two (or more) have gone by...