That doesn't seem correct. At least, I have never heard of a SW book with that exact title.
Drew Karpyshyn's new book, just came out: Annihilation. It's supposed to take place after our stories in the game and it's all about Theron Shan and his exploits fighting against a former apprentice of Darth Malgus, or something like that. That's about all I know because I have no interest in Satele or Theron, I read The Lost Suns comic and thought it was utter crap. Obviously just a personal opinion.
To the OP, Darth Gravus is the NPC for the Imperial Taris planet quest line. Also, this should have been posted in Story & Lore or Star Wars Discussion were you would have gotten the responses you were probably looking for because those are the two sections where people interested in this stuff congregate to have nice discussions about story and lore.