Bradygames or Primagames always release strategy guides before the game comes out, or during its release. And they always suck. They are overpriced, often poorly edited, and almost always wrong on many details/stats.
In an age of online encyclopedias of hints or strategies(Gamefaqs, etc.), fansites(Civfanatics, etc.), and forum communities(here, etc.) can be constantly updated by people interested enough in the subject to do so on their own free time, I can't see why anyone would pay for those worthless books. Print out an online FAQ if you want a hard copy, or save them to disk if you don't want to tie up your phone line looking at them.