BBY/ABY is used to position items along the Star Wars Timeline. BBY refers to Before the Battle of Yavin. ABY refers to After the Battle of Yavin. The Battle of Yavin in Episode IV: A New Hope occured in 0 BBY/ABY.
The Youtini Expanded Universe Ranking system is a 1-5 scale that ranks EU book quality, difficulty, and importance. Books closer to Level 1 are easier to read and understand, more important, and of higher quality.
DARTH VADER intends for the Empire to hold no secrets for him — or from him. Which means it is time to dig into the pet project of GOVERNOR WILHUFF TARKIN and ORSON KRENNIC: the massive battle station being built on GEONOSIS. Opportunity arises when the project is hindered by sabotage from unknown forces. THE EMPEROR calls on his dark enforcer to root out the source of treachery that threatens to destabilize the Empire's galactic ascent.