This really is a very good book and I'm going to recommend it to a librarian friend of mine who is responsible for selecting graphic novels for Sunderland City library.
Divided into 10 categories, each one has an introduction followed by the 10 most important titles and then the rest. Each title has a synopsis and brief critical appraisal, an age rating, a colour reproduction of the cover and, sometimes, samples of the artwork. The indexes are very useful being by: age range, writer, artist, and title.
As with all books of this type, you'll wonder why some titles were included and some of your own favourites weren't, but that's all part of the fun of reading it.
As for how effective it is, I've bought ten titles listed and only financial restraints have stopped me from ordering more. For the moment.
Highly recommended.