I bought the strategy guide the week before release. A few things are wrong in it since I have played the game, and it is riddled with spelling and wording mistakes. Also I believe they rewrite it a few times because it mentions the date its printed on the back, so they may update it every now an then, though I doubt they have yet. Reading it before the game came out may or may not have helped me with the game, I cant say for sure. I know I wouldnt buy it now though. Its basicly the same thing as the manual, except it has a small paragraph or two about strategies with each leader. It also talks about certain victory condition strategies.
One glaring thing that is wrong in it is that it said deals can not be canceled no matter what, even if you declare war. Everytime I declare war my deals are all canceled.