If the first book reminded me of 24, the second book is even more similar to the hit TV show, taking place in the White House, and actually occurring over a 24-hour period. I, Q: The White House contains slightly less violence than the first novel, so might be suitable for slightly younger audiences. However, terrorism is still a major theme, which would probably be scary and confusing to a reader too young to be able to handle the violence. As the title suggests, this story takes place in the White House. The President has two kids, Brittany, a teenager who has been fulfilling the social responsibilities of the First Lady since her mother's death, and PK ("President's Kid"), age 10, who is wise beyond his years.
The White House is always an interesting setting, because I think people wonder what it would really be like to live there.
Angela is getting closer to figure out the details about her mother's past, but she and Q are still in danger as they have to help figure out who the mole in the White House is.
I think that this series (I've read the first two books) is a wonderfully unique new offering for kids age 11 and up. There is some violence and the theme of terrorism, but especially if your child watches any sort of thriller/espionage type show on TV or in the movies, it isn't going to be too intense for them. There are guns and some fighting and even killing, but it is done in an age-appropriate way, especially if you think of it as a war story.
These books captured my attention as well, and so if you are an adult reader who enjoys thrillers, but wants to avoid the language and gore that does usually come with those, you should look into these books for yourself.