Thinking About Time: James Valentine, Jumpman Rule 2; Don't Even Think About It!>, (Sidney: Random House, 2003)
In this second book Jules and Genevieve are dragged into the future because someone is messing about with time and breaking the very first rule. "Don't touch anything!"
It turns out that Quincey Carter One is using their old friend Theo Pine Four to cover up Carter's plans to rescue lost things from Earth's past... pizza for one.
Genevieve ends up dumped in the past and although she has to be rescued by Jules, she's gets herself to the position where she can be rescued. Jules and his brain have conversations about being a teenage boy which are delicious in their painfulness. Theo turns into a little less of a brat (but he starts from such a high level that he has a long way to go).
The joys of the book are the construction of a deep future. We only get to see the surface but Valentine continually drops hints that there is so much more out there. I also like the way he handles the tension between a high tech society and the tendency of most of its citizens to be users, not makers. As with the first book, there is also quite a lot of time spent just thinking about the nature of time and time paradoxes.