I have read both of the now released books from Fate of the Jedi series Abyss and Omen .
Abyss (the first one I think) was slow and a little hard for me at times, but i prefer lots of action all throughout the book. as the first book in a new series, it followed the basic pattern well. descriptive and intriguing and just enough story to make you want to read the next book. it had a good action sequence in the first few chapters and then kind of died off for a few chapters.
they basically tell you all you need to know of the story spoiler wise over on the wookieepedia site. just search for the book series or title.
And the short story about the lost tribe of the sith that was available for download was a part of the new book... kind of. at least it involved the lost sith from the vessel OMEN.
and it involved the sith ship/eyeball with wing shaped training orb that was pretty predominant in the last few books of the last series.
Spoiler...the next book will take Luke and Ben into the Maw to face a new sith threat or some such. And the planet bound survivors of OMEN are now a spacefaring tribe of sith unaware of the ONE SITH that were in the background of the last series.
if the book reading is too much, check out the bits on Wookieepedia. and all the other info.
only bad thing is you have to read that too...
