I decided to avoid the boards here until I read the book for myself, and I'm glad I did. I finished the book earlier this week and absolutely loved it, with a few minor complaints here and there that weren't substantial enough to ruin anything for me.
As for Revan's mask
being worn as a light-sider, I actually have no problem with this. He wore the mask during the Mandalorian wars prior to turning to the dark-side. Granted, the image of Revan in the mask is absolutely associated with his time spent as a Sith Lord, but Revan did wear the mask before he was Sith.
My main issue with the book was with the Emperor's ability
to suck all the life (and force) from an entire planet, as I felt this egregiously amplified power had already been dealt with in TSL (Darth Nihilus). I know there were some minor differences between the two acts but they were too similar for the reveal on Nathema to warrant the shock factor that Karpyshyn was aiming for. If we are to believe that this act was so atrocious that even Sith Lords find it appalling (Nyriss, Scourge, and other members of the council), it needs to be something we haven't seen before to fully buy into it.
This book has got me even more excited to play TOR now, which was almost definitely the goal in releasing it. I hope there's more interaction with Meetra and Revan to come.