Paperback: 368 pages
Publisher: Ace Books; Reprint edition (24 April 2007)
My guess is that this is a follow-up to Red Thunder by the same author, though I didn't find the existence of a strong back story too distracting.
I first read Varley when his The Ophiuchi Hotline came out, many years ago now, and have followed his Eight Worlds scenario. But this isn't one of them. This could be Varley channelling Heinlein (and the presence of a major character named Jubal is a little suspicious in that regard).
Mars is the new ... Mars? At any rate, there has recently been a return to that planet for Science Fiction writers, and this is Varley doing so. Our PoV character is a native of Mars, one Ray Garcia-Strickland, a teenager who was one of the first humans born there. His parents run the Red Thunder hotel, catering to rich tourists who want to have visited Mars, brought there by the new technology that provides almost unlimited power from a little-understood science.
And then something horrible happens. Something moving at near light-speed draws a line across the Atlantic, causing a tsunami that wipes out much of the US East Coast, reducing the US to political chaos, but also possibly wiping out Ray's Florida-based relatives. So off the Mars-based family goes to look for and perhaps rescue them.
(Interestingly, the early drafts had the tsunami in the Indian Ocean, not the Atlantic. Understandably, when the real Indian Ocean tsunami happened, Varley didn't want to feel he was trading on that.)
About halfway through, the initial plot has apparently completed, and then a totally un-signposted second story swings into action, as mysterious invaders from Earth conquer Mars. This second story seems totally unconnected to the first for quite a while, before the links finally start being made, and the real reasons for everything become apparent.
A pretty good stab at a Heinlein juvenile. Lousy cover, though.