I enjoyed the premise of the book. Taking Nicholas Flamel and turning him and John Dee into contemporary characters is fascinating. I also enjoyed the concept of the 'Elders' and how they are the old gods of mythology, which is a neat way of explaining the presence of them in modern times and being able to icorporate gods from all types of world mythology.
The book was well paced, the characters likable and the little easter eggs of knowledge really interesting. However, I have to say that I didn't enjoy it as much as other mythology-for-modern-times young adult books, like Rick Riordan's. I can't put my finger on it but it's probably to do with the author's writing style. It was less action and more description, and I just felt that I wanted to be excited more.
In any case, I am looking forward to the next book in the series when I get around to it. I expect that the series will get better with each book.