Exactly how steamy is this story?
PG-13
Steaminess is certainly present in Timescape, although it is tempered to a PG-13, made-for-primetime-television coolness. Sex and sexually charged situations such as adultery and premarital hanky panky are all present, but they are written with a kind of beneath-the-sheet vibe. In other words, the details are more designed to advance themes and characterization than to be sexually explicit. Consider the following example:
He shaped her with his hands and tongue. She, in turn, guided and molded him. He thought he could sense in her sure moves and choices first this way and then that, past imprints of the lovers she had known before. Strangely, the thought did not bother him, thought [sic] he felt that in some way it should. Echoes of other men came from her. (7.58)
There's nothing too explicit in this sexual scene—depending on where you draw your personal explicit line—but dig a little deeper into the details, and you can see Benford setting up Gordon's character and his future difficulties with his relationship with Penny. The "imprints" and "echoes" have made Penny the woman she is today. In the same way, Gordon lost his virginity to Penny, so she is now molding him.
One of Timescape's major themes is considering the influence of the past on future events. The novel often takes the big picture approach—i.e. today's unsustainable marketplace habits will lead to disastrous climate change—but here it explores that same idea with two people behind closed doors.