This book adds some helpful information for fans of 'A Song of Ice and Fire', it's more that it is simply interesting and a lot of filler. As a long time ASoIaF nerd I enjoyed getting a linear time-line of Westeros and the world, as much as The Citadel knows of it, as well as a single collection of the legends and tidbits of back-history that have been littered throughout the books.
I could have done without the excessive two-page spreads devoted to the sisters of Baelor the Blessed, the mistresses of Aegon the Unworthy and other excuses to have portraits of generic hot women with moist parted lips and cleavage. I realize some nerds need their fantasy babes, but it could have been shoe-horned into the book a trifle more gracefully. Or at least get some more fantasy dudes in there. The ones who were pictured seemed to wear a lot more layers than the ladies and were more likely to have "a great personality and good hair", just saying. Overall though, the art was well selected. I'm not familiar enough with the card game to know if the art was pulled from Fantasy Flight or was commissioned for the book. Probably a mix of the two.
The conceit that this was a text written by a maester for presentation to the Iron Throne was a nice touch, it allowed the history to gloss over certain aspects and gave plausible deniability to not revealing key plot and historical details to readers. I dislike any delay to the series itself, but as we're at almost 21 years since the first book came out (and 16 since I began reading them), I'm resigned to the fact that my bitch George R.R. ain't what he used to be, and the books will arrive when they arrive and griping about it on the internet won't make them come any faster.
I waited awhile to read it, but I devoured it. This isn't a must-read, but if you're a nerd you'll love the glut of information.