The book is typical Doctorow standard - packed with great ideas, a neat plot and well-drawn characters. It details a city's slide into paranoia and fear after a terrorist attack, and the ways a small group of teenagers try to keep hold of their freedoms in the face of the government's determination to keep everyone safe/scared.
There's a tremendous amount of information in here: security systems, linux, encryption, the American constitution. It's like a Neal Stephenson book, entertaining, exciting, informative, but thankfully not 12000 pages long. This will drive up the numbers of kids wanting to become security consultants - it's even got an afterword by security guru Bruce Schneier. Great stuff.
UPDATED: now with linky goodness (it's hard to put links in when writing reviews on my phone).