87. Earthsong, by Victor Kelleher.

Two young adults are sent in a colony fleet from terraformed moons, back to a potentially inhospitable Earth, where contact has been lost with the previous human inhabitants, who did not leave with the rest. They're supposed to be the First Parents, but instead they nearly crash-land into a hostile world, left with a muddled computer and half a continent away from the rest of their supplies.

I remembered reading this book in high school, and enjoying it quite a lot, although it never my favourite book of Victor Kelleher's (That honour goes to Parkland, which I would have read instead, had my library been able to supply a copy). Reading it now, all I'm struck by is how the plot is really interesting in some ways, and really annoying in others. Their crashed computer/child-simulator is both frustrating and rather unique, and their interpersonal relationship is particularly Barbie-and-Ken-like, as if they don't get a choice in the matter. Which, I suppose, they don't. I'm left with the feeling that it could have been handled better, although the ideas behind it were excellent.