Aftermath is one of those books that would have been better as a radio show, not a book. It just sucks.
Tarkin was good and shows a lot of how Tarkin become what he was. It's solid.
Lords of the Sith was decent and showed how the relationship between Vader and the Emperor was still forming and molding.
All three suffered from minimalization -- reducing an entire galaxy to the level of making it seem like everything was only happening within a single star system. I continue to abhor the fact that writers ignore the scope and size of the sandbox in which they find themselves.