This is an excellent placing for a hardback Star Wars novel. Out of the two previous "Legacy of the Force" hardbacks, Sacrificemade its debut at #8, and Betrayalentered at #10.
Of course, the placing of a novel will vary according to the strength of the opposition, but this is a good position in comparison with other recent Star Wars hardbacks at well. Of Tim Zahn's two recent novels, Outbound Flight was at #7 and Allegiance was at #10, while James Luceno's Dark Lordentered at #11. Of Drew Karpyshyn's two Darth Bane books, Path of Destruction was at #11, while Rule of Two was at #12.
To find a higher-placing Star Wars hardcover in the charts, I think you have to go back to the Revenge of the Sith novelization by Matt Stover, which debuted at #2 in April 2005. I could be wrong, but with the exception of the movie adaptations, I believe this is the best placing in the Hardcover chart for any of the Star Wars novels published on the Del Rey contracts since 1999.