In addition to AI CheshireCat and human girl Steph, there's now a third protagonist, human girl Nell. They investigate apparently unrelated events that might actually all be caused by another AI. It's a really well-developed plot.
Both Steph and Nell have girlfriends. Nell lives with her father, her stepmother, her father's girlfriend and her stepmother's girlfriend. The latter also has another girlfriend. Basically, everyone has a girlfriend. :D