Customer Reviews
If you are going to buy one book about graphic novels... - By: IanW, 27 Aug 2008 
... then it probably shouldn't be this one. A better bet is 500 Essential Graphic Novels: The Ultimate Guide (500 Essential...). That said, this is a good second choice & complements the aforementioned book quite well.
The Rough Guide isn't as comprehensive, focussing in-depth on a top 60 graphic novels, referencing dozens of others. It also includes a short graphic novel about graphic novels, brief articles about icons of the genre (Eisner, Gaiman, Crumb, Moore, all the usual suspects & some not so usual), a piece about Manga, & quite a lot more.
As for how effective it is, it certainly brought to my attention a number of graphic novels I hadn't either considered or heard of before & I'm very glad it did.
Overall, not by a long way a definitive reference work, but not a bad introduction, & worthwhile. (The rating is really three & a half stars.)