A summary has reportedly appeared on the Science Fiction Book Club website and is available only to members, but someone at the Wookieepedia cut and pasted it.
VERIFIED: Paula logged into the SFBC and this is indeed the one they have posted.
The club writes their own summaries (check out the different Betrayal blurbs at SFBC and Random House) so it’s not too surprising that this is different from the last. (Which still hasn’t been confirmed – they’re keeping a tight lid on this one.)
It’s a long one, so spoilers are under the cut. Click and highlight at your own risk.
The war between the Galactic Alliance and the Corellian Confederation is building to a boiling point. Now the fate of the galaxy hangs on what is about to happen among a lonely cluster of asteroids. At Nickel One, base of the Verpine munitions industry, Jacen Solo assembles a fleet that can crush the Jedi Coalition. But even with the Imperial Remnant’s troops at his command, he may soon find himself outmatched…
Luke Skywalker knows the Jedi will never leave the hidden base at Shedu Maad alive unless they hunt down and kill Jacen Solo. But Luke, tainted by his killing of Lumiya, Dark Lady of the Sith, could fall to the dark side if he goes after Jacen himself. Having finished her training with Boba Fett, Jaina Solo realizes she’s the only one who can bring her brother down. So she sets off to finish what Mara Jade Skywalker started — unaware that Luke is using his Force abilities to mask her with his image. As Jacen’s Remnant fleet collides with Confederation and Mandalorian forces at Nickel One, a battle-royale explodes at Shedu Maad. Now, only a fatal clash between the Dark Lord of the Sith and the Sword of the Jedi may turn the tide of war…
I logged in to SFBC and that is, indeed, the summary that is up there.